(44) باب أَعْضَاءِ السُّجُودِ وَالنَّهْىِ عَنْ كَفِّ الشَّعْرِ، وَالثَّوْبِ، وَعَقْصِ الرَّأْسِ، فِي الصَّلاَة
Ibn Abbas reported that the Messenger of Allah (ﷺ) 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.
Reference: Sahih Muslim 490 d
In-book reference: Book 4, Hadith 260
USC-MSA web (English) reference(deprecated numbering scheme): Book 4, Hadith 994