Ahmad ibn Muhammad ibn Isa narrated from Ali ibn al-Hakam, from Uthman ibn Abd al-Malik, from Abu Bakr al-Hadrami, who said: I said to (Imam) Abu Ja‘far عليه السلام, peace be upon him: “What is the limit of bowing and prostration?” Imam عليه السلام said: “You say ‘Subhana Rabbi al-‘Azim wa bi-hamdih’ three times in bowing, and ‘Subhana Rabbi al-A‘la wa bi-hamdih’ three times in prostration. So whoever omits one has omitted one-third of his prayer, and whoever omits two has omitted two-thirds of his prayer, and whoever does not perform tasbih, then he has no prayer.”