Sahih al-Bukhari, Book 77, Hadith 122 (In-Book) ⓘ
Narrated Qatada: l asked Anas bin Malik about the hair of Allah's Messenger. He said, "The hair of Allah's Messenger was neither much straight, nor much curly, and it used to hang down till between his shoulders and his earlobes.
حَدَّثَنِي عَمْرُو بْنُ عَلِيٍّ، حَدَّثَنَا وَهْبُ بْنُ جَرِيرٍ، قَالَ حَدَّثَنِي أَبِي، عَنْ قَتَادَةَ، قَالَ سَأَلْتُ أَنَسَ بْنَ مَالِكٍ ـ رضى الله عنه ـ عَنْ شَعَرِ، رَسُولِ اللَّهِ صلى الله عليه وسلم فَقَالَ كَانَ شَعَرُ رَسُولِ اللَّهِ صلى الله عليه وسلم رَجِلاً، لَيْسَ بِالسَّبِطِ، وَلاَ الْجَعْدِ، بَيْنَ أُذُنَيْهِ وَعَاتِقِهِ.
also referenced under: Hadith 5905 (DarusSalam) & Volume 7, Book 72, Hadith 791 (USC-MSA)