it is illustrated by his prostrating when he prayed five units of prayer. He also instructed the person who is unsure whether he has added or omitted something to prostrate. These, then, are the causes mentioned in the Prophet’s words, peace and blessings be upon him: an addition, an omission, or doubt. It has already been established that, in cases of omission and doubt, one prostrates before the closing salutation, and in cases of addition, after it.

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If these prostrations are obligatory and someone omits them, deliberately or forgetfully, whether they are due before or after the closing salutation, there are several views within the school of Ahmad and among others.

One view is that deliberately omitting those due before the closing salutation invalidates the prayer, whereas omitting them out of forgetfulness does not, just as with the first tashahhud and other obligatory acts. Omitting those due after the closing salutation does not invalidate the prayer under any circumstances, since they serve to remedy a deficiency after the closing salutation, and their omission therefore does not invalidate it. This is the view preferred by many of Ahmad’s followers.

Another view is that omitting those due before the closing salutation invalidates the prayer in either case. If someone omits them out of forgetfulness and remembers shortly afterwards, he performs the prostrations; if a long interval has elapsed, he repeats the prayer. This is transmitted as one report from Ahmad and is the view of Mālik, Abū Thawr, and others. This view is sounder than the preceding one. For if something is obligatory within the prayer and a person fails to perform it out of forgetfulness, he remains bound to fulfil it, even though he incurs no sin. The same applies to the prayer itself: if he forgets it, he performs it