Tolerance of hunger, the most obvious part of fasting, earns plenty of advantages for a devoted wayfarer journeying towards Allah's path from the point of view of enlightenment and knowledge of Allah (the Glorious, the Exalted), as well as his advancement in attaining spiritual perfection. This has been emphasized in plenty of narrations, and therefore it would be appropriate to quote first an example and later on to discuss about its wisdom. The Holy Prophet [s] has narrated:
"Engage yourself in self-struggle (Jihad-e-Nafs) through the means of hunger and thirst, whose reward is equivalent to the reward of those who participated in the armed struggle for Allah's sake. There is nothing more superior before Allah's sight than tolerating hunger and thirst during fasting."
"The one who tolerates more hunger as well as ponders deeply about Allah as compared to others, will be assigned higher Exalted positions before their Lord on the Day of Judgement."
Also, he said to Asma:
"O' Asma! If you may act in a manner that when the angel of death approaches you, he should find you hungry and thirsty. If you do it you will attain the most Exalted spiritual position, will join the ranks of prophets, will make the angels happy, and will earn the divine salutations for yourself."
"Keep your stomachs hungry and thirsty, and make your bodies used to hardships, perhaps your hearts will then have a chance of seeing Allah's glory."
Also, in the narration of Prophet's heavenly journey (Me'raj) the following have been narrated:
"O' Ahmad! Do you comprehend the outcome of fasting? 'No.' Replied the Holy Prophet [s]. 'The outcome of fasting is less eating and less talking.' Replied Allah, then explained the outcome of silence and less speaking as follows:
'The result of silence is wisdom; the result of wisdom is enlightenment; the result of enlightenment is certainty; and when a person attains the Exalted spiritual position of certainty, then he does not care how does he start his day, whether with ease or hardship, and tragedy or comfort. Such is the state of those who have attained the position of content, and whoever attains this position acquires three inseparable characteristics: thanks (shukr) not contaminated with ignorance, invocation (dhikr) not mixed with forgetfulness and love not mixed with the love of others.'
'Whoever loves Me in this manner does not intermingle the love of others with My friendship; I too love him and make others to love him; would make his heart's eyes opened, so that he could witness My Splendour and Majesty; would not deprive him from the knowledge and enlightenment bestowed by Me upon others; in the midst of night's darkness as well as during the brightness of the day would whisper and communicate with him, so that he becomes disgusted with other's company; would have him listen to My speech as well as the speech of My angels; My secrets which I keep hidden from others would become manifested upon him.
'Would saturate his wisdom with My enlightenment (ma'refat) and would sit Myself in place of his wisdom; would make the pang of death and its hardships easier for him so that he would enter Paradise with ease and comfort. When the angel of death would descend upon him would speak to him: Welcome! Welcome! Welcome! Allah is anxiously waiting for you.'
The narration continues:
At this point Allah would speak to him: 'This is My Paradise, make yourself at home, and this is My neighbourhood in which you would be dwelling forever.' Then the soul would say: 'O' my Lord! You have introduced Yourself to me and after identifying You I became detached with Your entire creation. By Your Splendour and Majesty I swear that in order to earn Your pleasure if I have to be slaughtered seventy times with extreme suffering and torture, even then Your consent would have been the most dearest and desirable thing for me.' At this point Allah would speak to him: 'I swear with My Splendour and Majesty that from now on there will never be any veil between Me and you, that you may see Me whenever you desire so; that is the way I treat my friends.'"
The above-mentioned narration clearly explains the merit and wisdom of hunger, and on this basis the learned scholars of moral ethics have described numerous advantages for hunger, some of them will be mentioned here as follows:
"Whoever keeps his stomach hungry his thinking culminates to the highest level, thus, making his reflections stronger."
Especially, the prime advantages are purity of heart, sharpness of mind and thinking, because, thinking is tantamount to ultimate result while our other actions and deeds are tantamount to preliminaries. Even thinking or meditating in itself is spiritual journey while the other actions and deeds constitute the preliminaries and background of this spiritual journey. It is in this background that the narration says:
"Meditating for even a single second is better than worshipping for seventy years."
With the above-mentioned introduction we may see the numerous advantages and important points including:
"O' ye who believe! Fasting is prescribed for you, even as it was prescribed for those before you, that you may ward off (evil)."
- Holy Qur'an (2:183)
is a proclamation, extremely honourable, esteemed, distinguished, and sweet, because, it is an invitation to sit upon the table full of His generosity and to attain the sacred spiritual station of His union (wasal) and countenance (laq'a).
"Fasting is not only renunciation of food and drink, while observing fasting your flesh, eyes, tongue, and in accordance with certain traditions even skin and hairs must observe fasting and must remain pious and ascetic."
Pondering about the above-mentioned explanation would reveal that, since Allah (the Glorious, the Exalted), has invited us for His benevolence, any sort of talk, action, and behavior which would make us farther away from divine presence, would be indicative of negligence on our part, and would not be complimentary to that. Therefore, from these considerations we should not like and approve it, because, sitting in this state upon the table of blessing of the One who has invited us and is knowledgeable about all our thinking, thoughts, and plans while He is caring about us and we are naive towards Him, He is remembering us while we are negligent towards Him, and He is looking towards us while we are turning our faces away from Him, of course, would be impolite and rude, and no wise person would tolerate such behavior from any of his friends.
But Allah (the Glorious, the Exalted), because of His special grace and favours towards His bondsman, has not considered these indecent behaviours and inexcusable negligence as forbidden (haram) and considering this negligence factor, has assigned obligations for His bondman which are far lesser in magnitude than their capacities. For the sake of their ease, have allowed them to observe only parts of obligations as much as they may, and has overlooked the portions not performed by them.
However, on the other hand, His great devoted servants don't allow themselves to behave in this manner with their Lord, rather in every deed whether compulsory or forbidden, act in a manner which suits with their servitude and bondage as well as is decent enough for the Divinity and Splendour of their Lord, and those who show negligence in this path, and do not care about the rights of their bondage and the divinity of their creator are regarded by them as damned and destitute.
Regarding fasting, what conditions Imam al-Sadiq [a] considers essential for the authenticity of fasting, some of them would be described here as follows:
"The fast observer should consider himself as Hereafter's traveller, should remain in the state of humility, fear, self-degradation, and like a servant fearing his master, should remain afraid of Allah; his heart should remain pure from defects and contamination, and his inner-self should be free from everything except Allah; must sacrifice his entire friendship and intentions for Him and must purify his heart from all other friendships except Allah's; must surrender his eyes and soul to Him; must commit his soul for His remembrance; must utilize his body in Allah's path and must keep it distant apart especially the tongue from all sorts of sins and indecencies. Whoever has observed these limitations had indeed discharged his obligations of fasting properly, and whoever has shown negligence to discharge these obligations has wasted his fast and would not be benefited from its reward."
We must think about musts which Imam al-Sadiq [a] in this narration has considered essential for a fast observer, so that we may appreciate the advantages and blessings incorporated therein. For example, a fast observer who consider himself as a Hereafter's traveller - a traveller who is nearing his final destination - obviously will not be interested in worldly allurements, and will not pay attention towards anything except collection of provisions for his eternal journey. Or for example, a fast observer who is in a state of humility and heart-brokenness would not be interested in anything, except attaching himself to Allah (the Glorious, the Exalted), and would be pleased with His remembrance.
And the fast observer who has surrendered his body and soul absolutely to Allah (the Glorious, the Exalted), wouldn't care for anything except Him, inevitably his soul and body, self and conscience, and his entire existence would be filled with Allah's remembrance, love, worship, and servitude. And the fasting of someone like him is the fasting of favourites. (I swear by Allah in the name of His favourite and friends that may He bless us with the grace of undertaking such a fast at least once in lifetime).
 dhikr: inducing or maintaining a state of Allah's awareness, especially by means of vocal or silent recitation of his Supreme Names. For details see Ayatullah Ibrahim Amini's Book: Self Building, pp. 277-284 [Tr].
 Imam al-Sadiq [a] (83/699-148/765): the son of the fifth Imam, he lived in an increasingly favourable climate and was able to teach openly in Madina. Large numbers of scholars gathered around him to learn, including such famous Sunni figures as Imam Abu Hanifah, the founder of the one of the four Sunni schools of law. Towards the end of Imam Ja'far's life severe restrictions were placed upon his activities, as a result of growing Shi'ite unrest. More traditions are recorded from him than from all the other Imams together. He is so important for Twelve-Imam Shi'ite law that it is named the Ja'fari School after him. He is buried in the Baqi Cemetery in Madina. Ja'far's fame for religious learning was great, greater than that of his father or of any other Twelver Imam except for 'Ali bin Abu Talib [a] himself, perhaps the earliest historical reference presenting Ja'far as one of the most respected and highly esteemed personalities of his epoch, and as having profound knowledge and learning, is Ya'qubi's statement that it was customary for scholars who related anything from him to say: "the learned one informed us". Even the famous jurist of Medina, Imam Malik bin Anas, is reported to have said, when quoting Ja'far's traditions: "the Thiqa (truthful) himself told me that..." Similar compliments for Ja'far are attributed to the Imam Imam Abu Hanifah, who is also reported to have been his pupil. Al-Sadiq's [a] knowledge was great in religion and culture, he was fully informed in Philosophy, he attained great piety in the world, and he abstained entirely from lusts. He lived in Madina long enough to greatly profit the sect that followed him, and to give his friends the advantage of the hidden sciences [Tr].