Nadhr is a vow, a voluntary undertaking, of an act of virtue, as binding one's self in gratitude for some special favor prayed for. It is a solemn promise to God.
(a) Nadhr al--bir (Shukr, Thanks) - if a particular wish is fulfilled then to undertake to do an act of virtue.
(b) Nadhr istidfa’ al-baliyah - for removal of a hardship or difficulty.
(c) Nadhr al-zajr wa al-tanbih - Nadhr for reprimanding oneself on committing a sin, e.g., If I backbite someone then I shall be bound to pray two rak’at of prayer.
(d) Nadhr al-tabarru’, - It is a Nadhr without any of the above conditions; e.g., to bind oneself to pray Salat al-tahajjud during the month of Ramadan for the sake of Allah.
Nadhr should be performed In the following manner:-
(1) A Nadhr should be kept for the sake of Allah. It is essential to say "lil-Laahi ‘alayya" (It is, for Allah, upon me to do so) whilst doing Nadhr.
(2) A person doing Nadhr must be adult and sane; and should do Nadhr with his own free will.
(3) If an extravagant person, or one who is prevented by Shari’ah to deal in his property or wealth does any Nadhr involving money or wealth it is not valid.
(4) If a husband asks his wife not to keep Nadhr and whilst performing Nadhr the rights of the husband are likely to be encroached upon, then the wife cannot possibly keep such a Nadhr. However, if the husband has granted his permission then he cannot stop his wife from performing the Nadhr.
(5) Whilst doing niyyah of a Nadhr, one should be capable of performing the said Nadhr. Otherwise the Nadhr is void. For example, if one does a Nadhr that he will go to Karbala on foot, and it is out of his bounds, then such a Nadhr is void.
(6) A Nadhr cannot be kept to give up any obligatory or recommended act or to carry out any
makruh or haraam act because such a Nadhr is void.
(7) A Nadhr should always be performed according to the original Intention. For instance, if one keeps a Nadhr to give charity or recite prayers on a particular day, then it should be performed on that very particular day and should not be postponed to any other day.
(8) If a person keeps a Nadhr to fast on a particular day and he intentionally does not fast on that day, then he shall have to keep qadha and at the same time pay kaffarah. However, if he is prevented from fasting on that particular day because of a genuine reason, e.g. if he falls sick, or travels for Hajj, then he shall have to keep qadha only; there is no kaffarah on him.
(9) If one keeps a Nadhr to give some money for the shrine of an Imam or a martyr or any other pious person, then it is ihtiyat wajib to use it in its construction, light, etc.
(10) If the Nadhr is kept for an Imam or martyr or any Imam zada, (e.g., if my patient becomes well, then I will give as Nadhr, for the sake of Allah, shs. 100/-, to Imam Husain A.S.), then if he had a niyyah to use that money in a particular purpose (e.g. construction of an Imambargah}, then it must be used for that purpose.
And if at the time of doing niyyah of that Nadhr he did not specify a particular use, then it is called "Nadhr al--mutlaq" (unspecified Nadhr); and in this case the money should be used in a purpose which has some connection with that Imam or martyr. For example, for the needy pilgrims to his shrine, or the construction of his tomb, etc.
(11) The money of Nadhr al--mutlaq may also be used for the purpose of spreading and/or strengthening the religion, and for the help of poor Shi’ah.
(12) When one wants to spend the money of Nadhr (mentioned in Nos. 10 and 11), it is better to do niyyah that one is using it on behalf of the Imam or martyr concerned and that its reward is for that Imam or martyr.