Sunan an-Nasa'i, Hadith 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 " .
also referenced under: Book 28, Hadith 13 (In-Book) & Volume 4, Book 28, Hadith 3603 (DarusSalam)