Sahih Muslim · Hadith 6213
The Book Pertaining to the Excellent Qualities of the Holy Prophet (may Peace be upon them) and His - كتاب الفضائل
حدثنا شيبان بن فروخ، حدثنا جرير بن حازم، حدثنا قتادة، قال قلت لأنس بن مالك كيف كان شعر رسول الله صلى الله عليه وسلم قال كان شعرا رجلا ليس بالجعد ولا السبط بين أذنيه وعاتقه .
Qatada reported: I asked Anas b. Malik: How was the hair of Allah's Messenger (may peace be upon him)? Thereupon he said: His hair was neither very curly nor very straight, and they hung over his shoulders and earlobes.
Gradings are classical jarḥ-wa-taʿdīl, name-matched to a rijāl index (not individually re-verified).