—acts fall into “three” categories: obedience, disobedience, and permissible conduct. If someone swears to do something permissible or to refrain from it, expiation is prescribed by consensus.

The same applies if the oath concerns doing something disliked or abandoning something recommended. This is what is mentioned in Allah’s words:

“Do not make your oaths by Allah an excuse for not doing good, being mindful of Him, and making peace between people.”

If, however, the oath concerns performing an obligation or refraining from something forbidden, then fulfilling it is impermissible by agreement; rather, expiation is obligatory according to the great majority of scholars. Before expiation was prescribed, someone who swore such an oath was not permitted to fulfil it, nor was there any expiation that could relieve him of the consequences of breaking it. Rather, whether he fulfilled it or not, he would be guilty of a sin for which there was no expiation. This is comparable to vowing to commit a sin, according to those who hold that no expiation is prescribed for such a vow. The same applies if the oath concerns performing an act of obedience that is not obligatory.

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As for an oath expressed as a vow, known as a “vow of obstinacy and anger,” an example is saying, “If I do such-and-such, I must perform Hajj,” or “my wealth shall be given in charity,” or “I must fast,” intending thereby to deter oneself from that action. Another example is saying, “If I do not do such-and-such, I must perform Hajj,” or something similar.

Most scholars—including those of Mecca, Medina, Basra, and Kufa—hold that expiation for an oath suffices. This is the position of the hadith jurists, such as al-Shāfi‘ī, Ahmad, Ishāq, Abū ‘Ubayd, and others. It is also one of the two positions reported from Abū Hanīfa, and is the later report from him.