catches a rakʿah has thereby caught the whole prayer,” along with what Ibn Khuzaymah recorded (3/45) on the authority of Abū Hurayrah, traced back to the Prophet: “Whoever catches one rakʿah of the prayer before the imam straightens his back from bowing has caught that prayer.”

The proof for the second situation is the marfūʿ report related by Ibn Khuzaymah (3/57): “If you arrive while we are in prostration, do not count that as anything.”

3 – Whoever joins the imam while he is seated or prostrating, even though he has not caught the rakʿah, still gains the reward of that very act—an act of worship in its own right—as well as the merit of following the imam and the virtue of hastening to prayer as soon as he enters the mosque.

4 – The scholars have outlined the rulings for a latecomer according to the posture in which he finds the imam:
• If the imam is prostrating or sitting, the follower suffices with the opening takbīr (takbīrat al-iḥrām), descends with him without another takbīr, and omits the opening supplication; he should hasten to match the imam’s posture at once.
• If he finds the imam standing, he performs what is recommended upon entering the prayer: the opening supplication, seeking refuge with Allah, and Qurʾān recitation.
• If he finds the imam bowing, he utters the takbīrat al-iḥrām, which counts for the takbīr of bowing as well. If, in addition to the iḥrām, he pronounces a second takbīr for the bowing, that is preferable.