deliberately must repeat the prayer as long as that remains possible—that is, as long as it can be repeated within its prescribed time. This is the position of Mālik, al-Shāfi‘i, and Ahmad.

Mālik and Ahmad, however, say that prayer may contain an obligatory act whose requirement is waived if it is omitted forgetfully, with the prostrations for forgetfulness serving as compensation for it. According to both of them, the prostrations for forgetfulness are obligatory.

Al-Shāfi‘i, by contrast, says that omitting any obligatory act invalidates the prayer, whether the omission is deliberate or inadvertent. According to him (1), the prostrations for forgetfulness are not obligatory, for anything that may be omitted forgetfully without invalidating the prayer (2) is neither obligatory nor such that its omission invalidates it.

Most scholars—including Mālik, Abū Hanīfa, and Ahmad—hold that the prostrations for forgetfulness are obligatory. They say that the Prophet—may Allah bless him and grant him peace—commanded them, and a command entails obligation.

They also say that any addition to the prayer which, if made deliberately, would invalidate it does so by consensus. Examples include deliberately adding a fifth unit of prayer or deliberately concluding the prayer with the salutation before completing it. If, however, a person does this inadvertently, he performs the prostrations for forgetfulness, as established by the Sunnah and consensus.

Thus, these prostrations are prescribed for an addition that does not invalidate the prayer when made inadvertently, although it does invalidate it when made deliberately. The same applies to an omission from the prayer, for the prostrations are sometimes performed for an addition and at other times for an omission. An example is the Prophet’s prostration—may Allah bless him and grant him peace—when he omitted the first tashahhud (testification of faith). If someone were to omit it deliberately, his prayer would be invalid according to Mālik and Ahmad.

As for Abū Hanīfa, he deems obligatory (* in prayer certain acts whose omission does not invalidate it (3)—not (4) whether omitted deliberately or inadvertently. He says that a person who omits them has acted wrongly, as in the case of composure during prayer and the recitation of al-Fātiha.