(48) The Book of Adornment
كتاب الزينة من السنن
(9) Chapter: Letting the Hair Grow
(9) باب اتِّخَاذِ الشَّعْرِ ‏‏
Sunan an-Nasa'i 5060 
It was narrated that Al-Bara' said:
"I have never seen anyone who looked more handsome in a red Hullah than the Messenger of Allah [SAW], with his long hair that came down to his shoulders."
أَخْبَرَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ عَمَّارٍ، قَالَ حَدَّثَنَا الْمُعَافَى، عَنْ إِسْرَائِيلَ، عَنْ أَبِي إِسْحَاقَ، عَنِ الْبَرَاءِ، قَالَ مَا رَأَيْتُ أَحَدًا أَحْسَنَ فِي حُلَّةٍ حَمْرَاءَ مِنْ رَسُولِ اللَّهِ صلى الله عليه وسلم وَجُمَّتُهُ تَضْرِبُ مَنْكِبَيْهِ ‏.‏
Grade :  Sahih (Darussalam)
Reference : Sunan an-Nasa'i 5060
In-book reference : Book 48, Hadith 21
English translation : Vol. 6, Book 48, Hadith 5063