—he performs the missed part, continues from there, and makes sujud al-sahw (the prostration of forgetfulness). A Sunnah element is not resumed once the obligatory portion has begun, though one still performs sujud al-sahw for omitting it. A posture, however, is neither made up after being left nor does it require sujud al-sahw. If he is unsure how many rakʿahs he has prayed, he builds on certainty—that is, the lesser number—and then performs sujud al-sahw. Sujud al-sahw itself is a Sunnah, and its proper place is before the salām.

Section. There are five times during which no prayer is offered except one that has a specific cause: (1) after the Fajr prayer until the sun rises; (2) from the first appearance of the sun until it has fully risen and ascended the height of a spear; (3) when the sun is at its zenith until it begins to decline; (4) after the ʿAsr prayer until sunset; and (5) from the beginning of sunset until the disc has completely set.

Section. Congregational prayer is an emphatically recommended Sunnah. The follower must intend to follow, whereas the imam need not intend to be followed. A free man may pray behind a slave, and an adult may follow a youth who has not yet reached full maturity. The prayer of a man behind a woman is invalid, as is that of a proficient reciter behind one who is illiterate. Whoever prays anywhere inside the mosque while the imam is praying there, and is aware of the imam’s prayer, his own prayer is valid so long as he does not stand ahead of the imam. If he prays outside the mosque but remains close to the imam, is aware of his prayer, and no barrier intervenes, his following is also valid.

Section. A traveler may shorten a four-rakʿah prayer provided five conditions are met: that the journey be for a lawful purpose; that the distance be sixteen farsakhs one-way; that the prayer in question is itself a four-rakʿah prayer; and that he intend to shorten along with—