Sahih Muslim 11987
In-book no 4710حَدَّثَنَا يَحْيَى بْنُ يَحْيَى، قَالَ قَرَأْتُ عَلَى مَالِكٍ عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " الْخَيْلُ فِي نَوَاصِيهَا الْخَيْرُ إِلَى يَوْمِ الْقِيَامَةِ " .
It has been narrated on the authority of Ibn Umar that the Messenger of Allah (ﷺ) said: There will be great benefit in the forelock of the horses until the Day of judgment.