Sahih al-Bukhari 5906
Sahih al-Bukhari · Book 77: Dress · The curly hair
Narrated Anas:
حَدَّثَنَا مُسْلِمٌ ، حَدَّثَنَا جَرِيرٌ ، عَنْ قَتَادَةَ ، عَنْ أَنَسٍ ، قَالَ كَانَ النَّبِيُّ صلى الله عليه وسلم ضَخْمَ الْيَدَيْنِ، لَمْ أَرَ بَعْدَهُ مِثْلَهُ، وَكَانَ شَعَرُ النَّبِيِّ صلى الله عليه وسلم رَجِلاً، لاَ جَعْدَ، وَلاَ سَبِطَ.
The Prophet (ﷺ) had big hands, and I have never seen anybody like him after him. The hair of the Prophet was wavy, neither curly nor straight.