The Book of The At-Tatbiq (Clasping One's Hands Together)
12/40. Chapter:
On how many (parts of the body) does one prostrate on?
Sunan an-Nasai
أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا حَمَّادٌ، عَنْ عَمْرٍو، عَنْ طَاوُسٍ، عَنِ ابْنِ عَبَّاسٍ، قَالَ أُمِرَ النَّبِيُّ صلى الله عليه وسلم أَنْ يَسْجُدَ عَلَى سَبْعَةِ أَعْضَاءٍ وَلاَ يَكُفَّ شَعْرَهُ وَلاَ ثِيَابَهُ .
It was narrated that Ibn 'Abbas said: "The Prophet (ﷺ) was commanded to prostrate on seven parts of his body and not to tuck up his hair or his garment."
Reference : Sunan an-Nasa'i 1093In-book reference : Book 12, Hadith 65English translation : Vol. 2, Book 12, Hadith 1094