It is narrated from Sayyiduna Hudhayfah (may Allah be pleased with him) that the Prophet Muhammad (peace and blessings be upon him) used to recite « سُبْحَانَ رَبِّي الْعَظِيمِ » three times in his bowing (ruku‘) and « سُبْحَانَ رَبِّي الْأَعْلَى » three times in his prostration (sujud).