Hadith 638
In the lengthy hadith of Sayyiduna Rifa’ah (may Allah be pleased with him), these words are narrated: The Prophet Muhammad (peace and blessings be upon him) said to the man who had prayed and whom the Prophet (peace and blessings be upon him) instructed to repeat the prayer: "Then when you prostrate, make your face and both hands firm, until every bone (of your body) is settled and at ease in its place."