Sahih Muslim
The Book of Prayers (Kitab Al-Salat)
Book Number: 004 / Hadith Number: 994
Ibn Abbas reported that the Messenger of Allah (may peace be upon him) said: I have been commanded to prostrate myself on seven bones:" forehead," and then pointed with his hand towards his nose, hands, feet, and the extremities of the feet; and we were forbidden to fold back clothing and hair.