Muwatta Imam Malik Book of Jihad, Hadith 45

Yahya related to me from Malik from Nafi from Abdullah ibn Umar that the Messenger of Allah ﷺ held a race between horses which had been made lean by training, from al-Hafya to Thaniyatu-lWada. He held a race between horses which had not been made lean from the Thaniya (a mountain pass near Madina) to the mosque of the Banu Zurayq. Abdullah ibn Umar was among those who raced them .

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ نَافِعٍ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ، أَنَّ رَسُولَ اللَّهِ ﷺ سَابَقَ بَيْنَ الْخَيْلِ الَّتِي قَدْ أُضْمِرَتْ مِنَ الْحَفْيَاءِ وَكَانَ أَمَدُهَا ثَنِيَّةَ الْوَدَاعِ وَسَابَقَ بَيْنَ الْخَيْلِ الَّتِي لَمْ تُضَمَّرْ مِنَ الثَّنِيَّةِ إِلَى مَسْجِدِ بَنِي زُرَيْقٍ وَأَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ كَانَ مِمَّنْ سَابَقَ بِهَا .