Dhikr of Rukū‘ and Sajdah
Issue No.946- It is obligatory to utter dhikr in rukū‘, and as an obligatory precaution, one should recite “سُبْحَانَ اللّهِ” three times or “سُبْحانَ رَبِّىَ الْعَظِيمِ وَ بِحَمْدِهِ” once. It is also obligatory to utter dhikr in sajdah, and the obligatory precaution is to recite “سُبْحانَ اللّهِ” three times or “سُبْحانَ رِبِّىَ الْأَعْلى وَ بِحَمْدِهِ” once. The more he utters the dhikr the better it would be.