Sahih al-Bukhari, Hadith 1811 ⓘ
Narrated Al-Miswar: Allah's Messenger slaughtered (the Hadi) before he had his head shaved and then he ordered his Companions to do the same.
حَدَّثَنَا مَحْمُودٌ، حَدَّثَنَا عَبْدُ الرَّزَّاقِ، أَخْبَرَنَا مَعْمَرٌ، عَنِ الزُّهْرِيِّ، عَنْ عُرْوَةَ، عَنِ الْمِسْوَرِ ـ رضى الله عنه ـ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم نَحَرَ قَبْلَ أَنْ يَحْلِقَ، وَأَمَرَ أَصْحَابَهُ بِذَلِكَ.
also referenced under: Book 27, Hadith 6 (In-Book) & Volume 3, Book 28, Hadith 38 (USC-MSA)