Sunan an-Nasa'i, Hadith 1115 ⓘ
It was narrated that Ibn 'Abbas said: "The Prophet was commanded to prostrate on seven bones and was forbidden to tuck up his hair and garment."
أَخْبَرَنَا مُحَمَّدُ بْنُ مَنْصُورٍ الْمَكِّيُّ، عَنْ سُفْيَانَ، عَنْ عَمْرٍو، عَنْ طَاوُسٍ، عَنِ ابْنِ عَبَّاسٍ، قَالَ أُمِرَ النَّبِيُّ صلى الله عليه وسلم أَنْ يَسْجُدَ عَلَى سَبْعَةِ أَعْظُمٍ وَنُهِيَ أَنْ يَكُفَّ الشَّعْرَ وَالثِّيَابَ .
also referenced under: Book 12, Hadith 87 (In-Book) & Volume 2, Book 12, Hadith 1116 (DarusSalam)