(28) The Book of Horses, Races and Shooting
كتاب الخيل
(7) Chapter: Twisting The Forelocks Of Horses
(7) باب فَتْلِ نَاصِيَةِ الْفَرَسِ ‏‏
Sunan an-Nasa'i 3573 
It was narrated from Ibn 'Umar that the Prophet said:
"There is goodness in the forelocks of horses until the Day of Resurrection."
أَخْبَرَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، قَالَ حَدَّثَنَا اللَّيْثُ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، عَنْ رَسُولِ اللَّهِ صلى الله عليه وسلم قَالَ ‏ "‏ الْخَيْلُ فِي نَوَاصِيهَا الْخَيْرُ إِلَى يَوْمِ الْقِيَامَةِ ‏"‏ ‏.‏
Grade :  Sahih (Darussalam)
Reference : Sunan an-Nasa'i 3573
In-book reference : Book 28, Hadith 13
English translation : Vol. 4, Book 28, Hadith 3603