Sunan Ibn Majah, Chapter: The Chapters on Hajj

"The Messenger of Allah (saw) said, when he was atop his camel with the clipped ears in Arafat: 'Do you know what day this is, what month this is and what land this is?' They said: 'This is a sacred land, a sacred month and a sacred day.' He said: 'Your wealth and your blood are sacred to you as this month of yours, in this land of yours, on this day of yours. I will reach the Cistern (Hawd) before you, and I will be proud of your great numbers before the nations, so do not blacken my face (i.e., cause me to be ashamed). I will rescue some people, and some people will be taken away from me. I will say: "O Lord, my companions!" and He will say: "You do not know what innovations they introduced after you were gone.'"