Every matter which is accepted as part of Islam by most of the Sunni and Shi'a scholars is called Zaruri al-deen (Plural = Zaruriyat al-deen). It makes no difference whether that matter is proved by the Qur'an, hadith, ijma' (consensus) or rational proofs. Also it does not matter whether the subject concerns Usul al-deen or Furu al-deen or Islamic ethics and morality.
Zururiy al-madh-hab (Plural - Zaruriyat al-madh-hab): Every matter which is accepted as part of a madh-hab by most of the 'ulama of that madh-hab. For example, justice of God and infallibility of the twelve Imams are among the Zaruriyat al-madh-hab of the Shi'a Ithna 'ashari faith.
Anyone who refutes, rejects or has doubt about any of the Zaruriyat al-deen, becomes kafir and unclean although he might be claiming to be a Muslim. Likewise, anyone who refutes, rejects or has doubt about any of the Zaruriyat al-madh-had al-Shi'a, becomes Sunni, although he might be claiming to be a Shi'a or might be believing in the five Usul al-deen. If they die without repentance, then in the eyes of Allah, the Prophet and the Shi'as of Ahlul-bayt, the former is kafir and najis, and the latter a Sunni. The former is called murtadd (apostate) from Islam; and the latter a murtadd from Shi'a madh-hab.
As mentioned in a preceding chapter, a person who rejects a Zaruriy al-deen or Zaruriyat al-madh-had, becomes murtadd only if he knows that it is a Zaruriy-edeen or Zaruriyat al-madh-had, or if he is a man who cannot be oblivious of this fact - for example, if he is a learned man of religion or has lived in a place where religious discourses are often held.
If a man does not reject openly a Zaruriy al-deen or Zaruriy al-madh-hab, but his behavior shows that he does not believe in it (even if he does not disclose his disbelief because of fear), then he will be treated as a murtadd. For example if he, says insulting things about an Imam and yet professes to believe in him, or insults the Qur'an and yet says that it is incumbent to respect the Qur'an.
Here we mention some of the Zaruriyat al-deen which are accepted by both the Shi'as and the Sunnis to be an integral part of the Islam.
There is one God, Ever-living, All-powerful and Eternal. He is All-knowing, All-perceiving. He does whatever He does by His own will. He speaks and is Truthful. He does not enter into any body, needs nothing, and does no evil. It is He Who has created the universe and it is He Who sustains it.
It is Wajib to believe in the prophet hood of the previous prophets as well as of the Holy Prophet of Islam (s.a.w.a.). The prophets were free from kufr and (with some difference of opinion in details) they were sinless. Also they were free from every such defect in body or character which might create repulsion in people.
The Holy Prophet of Islam ascended to the heavens in mi'raj. The Qur'an is the word of Allah; hadith is an authentic source of shari'ah. The Prophet of Islam, Muhammad (s.a.w.a), is the last and final prophet; no prophet is to come after him.
It is wajib to believe in questioning in grave through Munkar and Nakir, and in the squeeze of grave. Angels, the Satan and the jinns do exist.
One day the world would come to end; then all people will be resurrected for judgement. The Day of Judgement is a fact and truth; transmigration of soul is a wrong idea. Everyone will get recompense of his/her good or bad deeds. Mizan (weighing scale), Hisab (reckoning of deeds), Sirat (Path, the bridge over the hell) are facts and truth; scrolls of deeds will be given in people's right or left hands. Shafa'at (intercession) by the Holy Prophet is a fact and truth. Repentance is wajib. Paradise and hell do exist even now.
Prayer, fast, hajj, zakah, jihad, enjoining good and prohibiting evil (with all their well-known details, like prayer's ruku: sajdah, number of rak'ah etc.) are wajib.
Virtue of truth, patience, contentedness; doing good to parents, relatives and neighbors. Evil of lie, back-biting, miserliness and disobedience of parents, besides many other virtuous and evil deeds well-known in Muslim society,
Zaruriyat al-madh-had al-Shi'a Ithna 'ashari: Some of the Zaruriyat of the Shi'a Ithna 'ashari faith are as follows:
God does not compel anyone to do a good or bad deed.
Imams are appointed by Allah. There are only twelve Imams after the Holy Prophet of Islam and they are his true successors; first of them is 'Ali (a.s.) and the last Imam al-Mahdi (a.s.). The twelve Imams and Bibi Fatima (a.s.) are infallible like the Holy Prophet (s.a.w.a.) from every sin and mistake from the beginning of their life to its end. The twelfth Imam, al-Mahdi, Muhammad son of the 11th Imam al-Hasan al-'Askari (a.s.), is alive and hidden at present; he will reappear when Allah allows him, before the Day of Judgement, and will establish the kingdom of God on the earth, filling it with justice and equity as it would have been filled of injustice and oppression.
"Hayya 'ala Khayril 'amal is part of adhan and iqamah; 'as-salatu khayrum minan nawm is not allowed in adhan or iqamah; mut'a marriage is lawful; a wife is not entitled to any share in land; as for other immovable properties like buildings or standing trees of a garden, she gets one-eighth (or one-fourth) of its market value, but not the thing itself.
All detail given in the chapters 3 (Usul al-deen) and 4 (Major Sins) are among Zaruriyat al-deen or Zaruriyat al-madh-had. Here only a few of them have been enumerated as example. There are many more Zaruriyat in Furu' al-deen and ethics, for which the readers should consult reference books.
Note: These details have been adapted from "Tosha al-Akherat" of late Syed Rahat Husayn Golpalpuri (Ex-Principal of Madrasatul-Waezeen, Lucknow), printed at Mujtabai Press, Patna; no date; pp. 23-29.