It is narrated from Sayyiduna Amr bin Awf bin Milhah al-Muzani (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Horses are separated from one another on the day they come down to water."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14094