Sunan an-Nasa'i, Hadith 1093 ⓘ
It was narrated that Ibn 'Abbas said: "The Prophet was commanded to prostrate on seven parts of his body and not to tuck up his hair or his garment."
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 .
also referenced under: Book 12, Hadith 65 (In-Book) & Volume 2, Book 12, Hadith 1094 (DarusSalam)