Double-facedness is the characteristic of the person who assumes an outward appearance and simulates a behaviour which is contrary to his inner state. For instance, one may give an impression of friendship and affection and pretend to be sincere and sympathetic, while in his heart he harbours an opposite feeling. Such a person displays sympathy and friendship in front of people, but is different in their absence.
Double-tonguedness is the quality of the person who praises and flatters people whenever he meets them, appearing to befriend them, but denounces them and speaks slanderously of them in their absence. Therefore, in the light of this description, the first quality may be specified as `behavioural nifaq' and the second as `verbal nifaq'. Perhaps the tradition refers to the evil of nifaq, since these two features are among the prominent and peculiar characteristics of the munafiqun (hypocrites).
Nifaq is one of psychic maladies and a vicious quality with its own specific signs and symptoms. It has also numerous grades and degrees, which, God willing, we shall discuss, together with their method of treatment, in the following sections.
Degrees of Nifaq:
It should be known that, like other vices and virtues, there are different degrees and stages of intensity and weakness of nifaq. In the case of any vice, if one does not take steps to cure it and does not persevere in the course of its treatment, it would lead him towards its extreme degrees, for there is no limit to the degree of intensity of vices and virtues. If man leaves his carnal self to its wishes, its innate propensity towards corruption, its instinctive appetite for worldly pleasures, the assistance of the Satan and the insinuations of the Khannas, all together incline it towards evil, and its vices, increasing day by day in intensity, reach the stage when they become an intrinsic, essential and ultimate quality of the soul. Then the regions of one's inner being as well as outer self come under its sovereignty and rule. And if the vice is characteristic of the Devil, such as nifaq and double-facedness, which are attributes of that cursed being-whom the Quran quotes as having said to Adam and Eve:
And he swore unto them (saying): Lo. I am a sincere adviser unto you. (7:21)
whereas in reality he was the opposite of what he claimed-the realm of your being will be annexed by the Devil's empire. When that happens, the ultimate form the spirit acquires will be satanic, and its inner essence and substance will also be satanic in nature. It is also possible that the external appearance in the next world will be of the Satan, though here you have a human form and appearance.
Thus, if man does not try to guard himself from this vice and allows his carnal self to act according to its wishes, within a short time all the means of control will be so thoroughly gone that all his labours and efforts will be put into the service of this vice. With whomever he will come in contact, he will meet and greet him double-facedly and with a double tongue. Socially, his intercourse and relations with others will become tainted with the vice of duplicity, dissemblance and hypocrisy. He will have no other objective except his own personal benefit and no goal except self-aggrandizement. Having trampled upon all the values of truthfulness, sincerity, magnanimity and courage, he will employ duplicity in all of his pauses and deeds, not abstaining from any indecency or perversion. Such a person is away from the domain of humanity and humanness, and on the Day of Judgement he will be raised as a member of the legions of the Satan.
All that was stated above was regarding the degrees of intensity and weakness of nifaq per se, but it also varies according to that to which it is related. Sometimes one practises nifaq in relation to the religion of God, sometimes with respect to virtues, sometimes in regard to righteous deeds and holy rites, and sometimes in ordinary matters of day-to-day life and common civilities. Also, sometimes one may act with nifaq with respect to the Prophet (S) or the Imams (A), and sometimes with regard to the awliya', the scholars and the believers. Sometimes one may behave with nifaq with Muslims and sometimes with God's creatures belonging to other communities and creeds.
Of course, these types of nifaq vary in the degree of their ugliness and indecency, though all of them are similar in that they share the quality of ugliness and indecency and are the buds and leaves of the same vicious tree.
Effects of Nifaq:
Nifaq and double-facedness, besides being an abominable, ignoble and vicious quality itself, which no decent person would like to adopt and whose possessor is not only excluded from the human category, but cannot be likened to any of the beasts as well, it is a cause of humiliation and ignominy in this world in front of one's fellows and friends, and brings about disgrace and punishment in the Hereafter also. As mentioned in the tradition, in the Hereafter such a person will be resurrected with two tongues of fire in his mouth. This will be a source of disgrace for him in front of the creatures of God and will bring about his infamy in the presence of His prophets, apostles and archangels. The severity of the punishment is also indicated by this tradition. Because, if the substance of the body becomes that of fire, imagine how severely it will be felt and what a great pain and suffering it will inflict. I seek refuge in God from its severity.
It is reported in another tradition that the Prophet (S) said that the double-faced person will come on the Day of Resurrection in such a condition that one of his two tongues will protrude from the back of his head and the other from the front, and both the tongues will be aflame, making his entire body ablaze with fire.'  Thereupon, it will be announced that he was double-faced and double-tongued in the world.
He will be known on that day by this vice of his, the following Quranic verse having become applicable to him:
... and sever that which Allah hath commanded should be joined, and make mischief in the earth; theirs is the curse and theirs the ill abode. (13:25)
Nifaq is source of many an evil and destructive trait, each one of which may bring about one's doom and eternal damnation. One of them is causing discord and sedition (fitnah), which, according to an express text of the Quran, is worse than homicide. Another is slandering (namimah), which is denounced by al-'Imam al-Baqir (A) in the following tradition:
(Entry to) Paradise is prohibited to slanderers who walk on the path of calumny (i.e. are habitual slanderers). 
The sins of slandering others and backbiting are worse than the sin of adultery, according to a statement of the Prophet (S), and are equivalent to subjecting a believer to torture, reviling him, and divulging his secrets; each one of which alone is enough to bring about one's destruction.
Let it be known to you that other bad habits which belong to the category of nifaq are: making gestures, allusions, winking, making signals with the eyes and so on-things that some persons do in order to mock some others, whereas they pose to be friendly and sincere in front of them. One should be very cautious of his own state and be careful of his deeds and behaviour, because the snares of the self and the designs of the Satan are very subtle, and there are very few people who are able to save themselves from them. It is possible that on account of an inappropriate act of beckoning or an improper winking one may be branded as double-faced and double-tongued. Perchance one may possess this bad habit as long as he is alive and imagine himself to be morally healthy, sound and pure. Therefore, it is essential for an individual to take care, like a devoted and sympathetic physician, of his spiritual and moral health and constantly keep an eye on his own deeds and habits, like a careful and vigilant nurse, and never fall short of his duty. He should know that none of the diseases of the heart is more concealed and elusive, and at the same time so fatal, than this disease, and no nurse should be more sympathetic and kind than an individual to himself.
Cure of the Disease of Nifaq:
There are two ways of getting rid of this greatly evil vice:
The first is to think about the harms that proceed from this vice, in this world as well as in the Hereafter. One should deliberate upon the matter that if he becomes known in this world for having this bad habit, he will be degraded in the eyes of his fellows and become infamous among his fellow human beings. They will avoid his company and he will be deprived of their friendliness. Moreover, he will fail to achieve any merit and to reach his higher goals. Thus it is necessary for a man of honour and dignity endowed with the conscience to purge himself of this ignominy that consumes honour, and not to allow himself to be entrapped in its disgraces. Besides, in the other world, which is the realm of the unveiling of secrets, where things that remained concealed from the eyes of people shall not be hidden, there, he will be raised a deformed, ugly creature possessing two tongues of fire and punished along with the hypocrites and devils. Therefore, it is incumbent upon a man of wisdom, who sees no good in it but harm, ugliness and abomination, to get rid of this vice.
The other treatment, which involves action, is another method of curing the self. It requires the individual to be extremely vigilant regarding his acts and pauses, and that he should act deliberately against his base wishes, wage a war against himself and try to improve his self inwardly as well as outwardly, in deed as well as in speech. He should abstain from affectation, coquetry and dissemblance in practice, and beseech the Almighty's help and assistance during this period to give him supremacy over his carnal self and its desires and to guide and accompany him in this undertaking. His mercy and grace towards His creatures are boundless, and whosoever advances towards Him wishing to reform himself, He extends His support and help to him.
If one perseveres in this for several days, it is hoped that the soul would become purified and the rust of hypocrisy and double-facedness will be removed from it. The mirror of his heart and his inner being will be cleansed of this vice, and it will be ready again to receive the favours and blessings of the Bestower. Because it has been established through rational proofs, and also confirmed by experience, that as long as man lives in this world, he is conditioned by the deeds and actions committed by him, and every one of his deeds, the pious as well as the vicious ones, leave their impressions and effects on the soul. If the deeds are pious and good, they leave a luminous and sublime effect; if not, a dark and negative impression is left on the soul. Thus, as a result, the heart is either rendered bright and luminous or dark and gloomy, according to the deeds. He is either grouped with the good and virtuous, or with the vicious and corrupt. Therefore, as long as we tarry in this house of action and this place of cultivation, we can freely steer our hearts in the direction of felicity or in the direction of wretchedness. We are hostages of our actions, about which the Quran says:
And whoso doth good an atom's weight will see it, and whoso doth ill an atom's weight will see it. (99:7-8)
Some Forms of Nifaq:
Let it be known to you, dear friend, that one of the forms of nifaq, double-facedness and double-tonguedness is nifaq with the Almighty, the King of kings, and the Bestower and the Nourisher, with which we are inflicted in this world but are not aware of it. Thick curtains of ignorance and folly and dark veils of the love of the self and the world have obstructed our vision in such a way that it is not possible for us to know our defects before the time of the divulging of secrets and the raising of these curtains and veils and before departing from this world of nature and saying farewell to this house of illusion and this zone of neglect and stupor. Although now we have receded into a state of physical stupor and obliviousness, and are intoxicated by the attractions of physical life and sensual existence, which beautify all moral and behavioural villainies in our eyes, the moment shall come when we shall wake up and come to our senses, and realize that there is nothing left for us to be done, that we have lost the opportunity-and have been branded as munafiqun, double-faced, and double-tongued, and resurrected with two flaring tongues or with two hideous faces. Then, even if we weep and wail, and yell out, "Lord, send me back into the world", the answer will come, "Never". Such will be the fate of our double-faced ness; while, in this life, you and I have been claiming faith in the Unity of God throughout, and professing to be Muslims and true believers untiringly, and even making ardent claims of His love.
If we are laymen, we boast of our faith in Islam, our sincerity of faith and our piety. If we belong to the class of `ulama' and jurisprudents, we pretend the highest degree of sincerity (ikhlas) and put forth claims to the wilayah and the khilafah of the Prophet (S). We imagine that the words uttered by the Prophet (S): (O God! Have mercy upon my successors), and by the present Imam (A) -may my soul be sacrificed for him: (Verily they are my proofs ....) and all other statements of the Imams (A) about `ulama' and fuqaha', to have been spoken about ourselves.
And if we belong to the class of scholars of philosophy and the rational sciences, claiming to possess true faith based on deductive proofs, we deem ourselves to be men of certain knowledge (`ilm al-yaqin), and those who possess `ayn al-yaqin and haqq al-yaqin, considering all others as possessing imperfect knowledge and infirm faith, and applying all the pertinent Quranic verses and traditions to ourselves.
And if we count ourselves among the mystics and men of `irfan, claiming mystic knowledge, ecstasies of love, states of annihilation in God and subsistence through Him (fana' fi Allah, baqa' bi Allah) and His vicegerency (wilayat al- amr), we apply such appellations, and whatsoever that appears to be attractive, to ourselves.
Thus, each one of our various groups claims some kind of high station by employing a vocabulary that it considers suitable for itself and for the display of its particular relation to the Truth. If this outward display complies with his inner reality and this appearance corresponds to his secret inward, he is of course truthful in claims and his blessed condition indeed deserves congratulations: (May the blessing do much good to him and to its other possessors). But if he is, like this writer, a deformed wretch, he should know that he belongs to the class of munafiqun and the double tongued. He should set out to treat himself and make use of the opportunity before it slips away, and do something about his unfortunate condition and the day of darkness and humiliation that awaits him.
My dear, you who claim adherence to Islam, there is a tradition in al-Kafi reported from the Apostle of God (S):
A Muslim is one whose hand and tongue spare all Muslims. 
What is the matter with us that we give ourselves the right to harass and hurt, by all possible means, our subordinates, and never hesitate to cause them inconvenience or to create problems for them? Or, if we cannot do any harm by our hands, why do we hurt them with the dagger of our tongue, by using derogatory language in their presence, or, in their absence, by opening their secrets, by slandering them and making false accusations against them? Therefore, we, whose hands and tongues do not spare Muslims, our claim of adherence to Islam contradicts our reality, and the state of our hearts is opposite to what our knowledge of Islam tells us. Hence we belong to the category of munafiqun and the double-faced.
O you who profess to adhere to the true faith and to submit your heart to the sovereignty of the Almighty! If you have full faith in the Oneness of God, and your heart is devoted to the worship of the One and yearns for the One, and that if you do not believe in the existence of any deity except God, if your heart mirrors your outward and your inner is true to your claims, what is wrong with you that you are so subdued and humble in front of the people? Why do you worship and idolize them? Is it for some other reason than this that you believe them to be powerful and influential, and you imagine their power and wealth to be of some consequence? Perhaps the only thing that you do not believe to be effective and active in this world is the Will and Determination of God Almighty. Aren't you humble and subdued in front of all the external phenomena, yet neglectful towards the really Powerful, the First Cause? Yet in spite of this state of mind, you assert your faith in the Unity of God! You should know that you are a foreigner to the community of believers, and belong to the group of munafiqun and the double-tongued and will be resurrected with them.
You who profess to be a genuine monotheist and of sincere piety, if you are really sincere and abstain from worldly pleasures only for the sake of God and His abode of bliss, what is wrong with you that you are so eager to hear people say in your praise that so and so is such a pious man, and are jubilant when someone says such a thing? Why are you willing to die for the company of the rich and affluent and flee from that of the poor and needy? You must know that neither your monotheism nor your piety are genuine. Your piety and abstinence are for the sake of the world, and your heart is not sincerely devoted to God. Your claims are false and you belong to the category of the double-faced and munafiqun.
And you who claim to be an appointee to the office of wilayah (leadership) by the Wali Allah (i.e. the Twelfth Imam) and to that of khilafah by the Apostle (S) of God, if your condition is in accordance with the specifications mentioned in the tradition of al-'Ihtijaj:
He who keeps his soul chaste, safeguards his faith, opposes his desires, and obeys the commands of his Master .... 
if you are yourself a branch of the tree of wilayah and risalah (prophethood), and if you are neither inclined towards the world, nor yearn for the nearness of kings, rulers and nobles, nor you are averse to the company of the poor, then indeed you deserve your name and title and you are certainly one of the proofs (hujjah) of God among the humankind; otherwise you are one of the wicked `ulama' and the munafiqun, and your plight is worse than that of the aforementioned group of people, and your deeds more abominable and your life far more wretched and miserable; since there is no ground for any plea or pretext for the `ulama'.
And you who claim to possess the Divine hikmah and the knowledge of the realities of the origin and the end (al-mabda' wa al-ma'ad), if you do possess the knowledge of the realities of causes and effects, and if in reality you know the forms assigned to men in Barzakh and the matters of heaven and hell, you should not have found peace for a while and should have spent each and every moment of your life in the construction of the life in eternity. You should have sought refuge from this world and its temptations. You know as to what sort of torments lie ahead and what darkness and severities await you. Yet why didn't you step out from behind the curtain of terms and concepts? Why haven't the rational demonstrations and proofs exerted any influence on your heart, even to the extent of the wing of a fly? Hence, in such a state, know that you stand outside the class of true believers and hukama', and on the Day of Judgement you will be resurrected in the ranks of munafiqun. Woe unto the man who spent his whole life arid energies in acquiring the knowledge of the metaphysical, yet could not overcome his intoxication and infatuation with the physical, so that not even one of the truths ever entered his heart!
And you who claim the gnosis of God, and speak of spiritual fervour, of wayfaring, of His love and your wish to annihilate yourself in the Divine Essence, if you are sincere in your devotion to God and belong to the category of ashab al-qulub, men of enlightenment with a record of virtuous past, then may it do you much good. Otherwise, inflated, theopathetic utterances (shathiyyat), pretentious ecstasies, and extravagant claims reveal only your self love and your -satanic tendencies, which are opposed to the love of God and godly fervour, for God says:
Verily, My awliya', under My vault (i.e. the sky), are known to none except Me. 
If you do belong to the category of the awliya' of God, His lovers and those absorbed totally in His love, it is indeed known to God. There is no need for you to boast about your high station in front of people. Do not distract the unsteady hearts of the creatures of God from their Creator, by inclining them towards a creature of His. Do not trespass upon the house that belongs to God. Know that those creatures are dear to God, and their hearts are valuable and precious they are to be employed in the service of God. Do not make a sport of the house of the Lord, and do not put your hands on His sanctities, for it has been said, (`Indeed the house has a Master'). Hence, if you are not true in your claims, you will be grouped with the double-faced and the men of nifaq. But let me stop here, since it isn't proper for a wretch like me to speak any further.
O you vile self of the writer, who make much pretence: do something about the dark days of your life and find a way out of your wretchedness. If you are really sincere and your heart agrees with your tongue and your inner intention is compatible with your outward appearance, why are you so heedless, your heart so blackened, and your lusts so indomitable? Why don't you think about the journey of death, which is so full of perils? Your days are past, yet you have not given up your lusts and desires. You have spent your days in satisfying lusts and in neglect and mischief. The time of your death draws near, yet you are enmeshed in your vicious deeds and entrapped in your indecent conduct. O preacher, who would not learn any lesson, you stand in the midst of munafiqun and the double-faced. Being one of them, it is feared that you will be resurrected with two tongues of fire and two faces of fire, if you continue in your present state.
O God, awaken us from this protracted spell of deep slumber, and bring us back to our senses from this state of intoxication and unconsciousness. Illumine our hearts with the light of faith and have mercy on us. We are not champions of this field. You Yourself succour us and deliver us from the talons of the Devil, for the sake of Your chosen servants, Muhammad and his undefiled progeny, upon all of whom be God's benedictions.
. Al-Kulayni, al-Kafi (Akhundi), vol. 2, p. 343.
. Al-Shaykh al-Saduq, 'Iqab al-'a'mal (Maktabat al-Saduq), p. 319.
. Al-Kafi, vol. 2, p. 369.
. Ibid., vol. 2; Fayd al-Kashani, al-Mahajjat al-bayda', vol. 3, p. 358.
. Al-Tabarsi, al-'Ihtijaj, vol. 2, p. 106; al-Hurr al-`Amili, Wasa'il al-Shi'ah, vol. 18, p. 99; al-Kulayni, op. cit., vol. 1, p.412; al-Shaykh al-Tusi, al-Tahdhib, vol. 6, p. 301; al-Shaykh al-Saduq, Man la yahduruhu al-faqih, vol. 3; al-Nuri, Mustadrak al-Wasa'il, vol. 3, p. 187 ; Shaykh Muhammad Hasan, al-Jawahir, vol. 40, p. 32.
. Ahadith qudsi. Source untraced.