- If a person takes an oath to do something or to refrain from doing something – for example, he takes an oath to keep a fast or to stop smoking – then in the event that he intentionally (ʿamdan) does not fulfil his oath, he will have committed a sin and he must give recompense (kaffārah). That is, he must either free a slave, or feed ten poor people (fuqarāʾ), or clothe them. And if he cannot do any of these, he must fast for three consecutive days.
- An oath must fulfil the following conditions [in order for it to be valid (ṣaḥīḥ)]:
1. the person taking the oath must be of the age of legal responsibility (bāligh), and sane (ʿāqil). He must also have an intention (qaṣd) to take the oath and must take it of his own volition (ikhtiyār). Therefore, an oath taken by a child, or an insane or intoxicated person, or someone who has been compelled, is not valid. The same applies [i.e. an oath is not valid] if it is taken by someone who in his anger took it unintentionally or did not take it of his own volition;
2. The act for which one takes an oath must not be unlawful (ḥarām) or disapproved (makrūh). And the act that one takes an oath to refrain from must not be an obligatory (wājib) or recommended (mustaḥabb) act. If a person takes an oath to do – or refrain from doing – something that is permissible (mubāḥ), in the event that doing it or refraining from doing it is something that would be preferred in the opinion of rational people or it is in the person’s worldly interest, the oath is valid;
3. A person must swear by one of the names of the Lord of the worlds that is reserved exclusively for His Holy Essence, such as ‘God’ and ‘Allah’. Alternatively, Allah may be invoked using words that describe attributes and actions exclusive to Him; for example, one can say, ‘I swear by the one who created the heavens and the earth.’ And if one swears by a name that is also used for a being other than Allah but it is used so frequently to refer to Allah that whenever someone mentions it the Holy Essence of the Lord comes to mind – such as swearing by the ‘Creator’ (al-Khāliq) or the ‘Sustainer’ (al-Rāziq) – this too is valid. In fact, if one swears by a name that only comes to mind when one is taking an oath – such as ‘The All-Hearing’ (al-Samīʿ) and ‘The All-Seeing’ (al-Baṣīr) – then again the oath is valid;
- One must verbally say the oath. However, if a dumb person takes an oath by using sign language, it is valid. And if a person who is unable to speak writes it down and intends it in his heart, it is sufficient. In fact, if a person who is able to speak writes it down, then based on obligatory precaution (al-iḥtiyāṭ al-wājib) he must fulfil it;
5. It must be possible for one to fulfil the oath. If at the time of taking the oath it is not possible for one to fulfil it but afterwards it becomes possible, it is sufficient. And if at the time of taking the oath it is possible for one to fulfil it but afterwards he becomes unable to fulfil it, then his oath becomes annulled from the time he became unable to fulfil it. The same applies if fulfilling the oath becomes so excessively difficult (mashaqqah) for him that he cannot endure what it takes to fulfil it. And if him not being able to fulfil the oath was due to his own free actions, or it was not due to his own free actions but he did not have a legitimate excuse (ʿudhr) for delaying the fulfilment of the oath when he was able to fulfil it, then he will have committed a sin and kaffārah is obligatory on him.
- If a father prevents his son from taking an oath, or if a husband prevents his wife from taking an oath, then any oaths they take are not valid.
- If a son takes an oath without the permission of his father, or if a wife takes an oath without the permission of her husband, the father and the husband can annul their oaths.
- If a person does not fulfil his oath owing to forgetfulness, necessity, or negligence, it is not obligatory on him to give kaffārah. The same applies if someone forces him to not fulfil his oath. Furthermore, if an obsessively doubtful person (muwaswis) takes an oath – for example, he says, ‘By Allah! I will engage in performing prayers now’ and due to his obsessive doubting he does not engage in performing his prayers, in the event that his obsessive doubting was such that he did not act of his own volition when he did not fulfil his oath, kaffārah is not obligatory on him.
- If a person takes an oath in order to establish that what he is saying is the truth, in the event that his words are indeed true, the act of taking such an oath is disapproved; and if his words are false, it is unlawful. In fact, a false oath that is taken in order to resolve a dispute is one of the major sins. However, if one takes such an oath in order to save himself or another Muslim from the evil of an unjust person, there is no problem; rather, it sometimes becomes obligatory to do so. Furthermore, if someone is able to employ equivocation (tawriyah) while being aware of doing so, then the obligatory precaution is that he must do so. Tawriyah is when a person intends a meaning that is contrary to the apparent meaning of what he says, i.e. what he says does not indicate what he intends [but at the same time it is not, strictly speaking, a lie]. For example, an unjust person wishes to harass a particular individual and he asks someone, ‘Have you seen him?’ Now, even though the person being asked saw him an hour ago, he replies, ‘I have not seen him’ and by that he means he has not seen him in the last five minutes.