It is narrated from Sayyiduna Khalid bin Urfutah (may Allah be pleased with him); he said: I saw the Messenger of Allah (peace and blessings be upon him) with his hands raised, supplicating: "O Allah, send blessings upon the horses of (the tribe of) Ahmas and upon its men."
Hadith Referenceالمعجم الكبير للطبراني / باب الخاء / 4095