What should a worshipper do if he remembers that he has not recited the surah after Al-Fatiha while he is descending for rukoo’ (before fully reaching the bowing position)?

Reciting a surah during prayer is a sunnah. Its place is during the standing posture (qiyam) after Al-Fatiha in the Fajr and Jumu'ah prayers, and in the first two rak'ahs of Dhuhr, Asr, Maghrib, and Isha prayers. Whoever forgets it and does not remember it until he bows for rukoo' has missed the chance to rectify it (by reciting it). He should perform the two prostrations of forgetfulness (sujood al-sahw) before the tasleem (final salutation).