It was narrated from Kathir bin 'Abdullah bin 'Amr bin 'Awf Al-Muzani, from his father, that his grandfather said:
“The Messenger of Allah ﷺ said: 'Start with the horses on the day that you bring (the animals to drink).' ”

حَدَّثَنَا إِبْرَاهِيمُ بْنُ الْمُنْذِرِ الْحِزَامِيُّ، أَنْبَأَنَا أَبُو الْجَعْدِ عَبْدُ الرَّحْمَنِ بْنُ عَبْدِ اللَّهِ، عَنْ كَثِيرِ بْنِ عَبْدِ اللَّهِ بْنِ عَمْرِو بْنِ عَوْفٍ الْمُزَنِيِّ، عَنْ أَبِيهِ، عَنْ جَدِّهِ، قَالَ قَالَ رَسُولُ اللَّهِ ﷺ " يُبْدَأُ بِالْخَيْلِ يَوْمَ وِرْدِهَا " .