Sayyiduna Rafi' bin Amr al-Muzani (may Allah be pleased with him) said: I came with my father while I was a small boy - Yahya bin Sa'id said in his narration: a young boy or somewhat older; and Ya'la said: five or six spans tall - at the Farewell Hajj, and there was the Messenger of Allah (peace and blessings be upon him) addressing the people while mounted on a white mule, and Sayyiduna Ali bin Abi Talib (may Allah be pleased with him) was conveying his words to the people. Some of the people were sitting and some were standing. My father sat down, and I made my way between the mounts until I reached the mule. I took hold of its stirrup and placed my hand on his (peace and blessings be upon him) knee, then passed my hand down to the shin until I reached the foot. Then I slipped my palm between the sandal and the foot, and even now it seems to me that I feel the coolness of his (peace and blessings be upon him) feet on my palm. These are the words of the narration of al-Umawi.
Hadith Referenceالمعجم الكبير للطبراني / باب الراء / 4443