Abu Dawud Book 4, Hadith Number 1951.

Narated By Rafi’ ibn Amr al-Muzani : I saw the Apostle of Allah (PBUH) addressing the people at Mina (on the day of sacrifice) when the sun rose high (i.e. in the forenoon) on a white mule, and Ali (Allah be pleased with him) was interpreting on his behalf; some people were standing and some sitting.