(44) باب أَعْضَاءِ السُّجُودِ وَالنَّهْىِ عَنْ كَفِّ الشَّعْرِ، وَالثَّوْبِ، وَعَقْصِ الرَّأْسِ، فِي الصَّلاَة
It was narrated from Al-'Abbas bin 'Abdul Muttalib that he heard the Messenger of Allah (ﷺ) say:
"When a person prostates, he prostates on seven part of the body: His face, his hands, his knees and his feet."
Reference: Sahih Muslim 491
In-book reference: Book 4, Hadith 262
USC-MSA web (English) reference(deprecated numbering scheme): Book 4, Hadith 995