Musnad Ahmad 25:1201

Abdullah ibn Bakr narrated to us, Hatim ibn Abi Saghir Abu Yunus narrated to us, from Amr ibn Dinar, that Kurayb informed him that Ibn Abbas said: I came to the Messenger of Allah (peace and blessings of Allah be upon him) at the end of the night, and I prayed behind him. He took my hand and pulled me, placing me beside him. When the Messenger of Allah (peace and blessings of Allah be upon him) turned to his prayer, I retreated. The Messenger of Allah (peace and blessings of Allah be upon him) prayed, and when he finished, he said to me: "What is the matter with me placing you beside me, and you retreat?" I said: "O Messenger of Allah, is it appropriate for anyone to pray beside you, while you are the Messenger of Allah whom Allah has given [what He has given]?" He said: So he was pleased with me, and he supplicated to Allah for me to increase me in knowledge and understanding. He said: Then I saw the Messenger of Allah (peace and blessings of Allah be upon him) sleep until I heard him breathing heavily (snoring). Then Bilal came to him and said: "O Messenger of Allah, the prayer." So he stood and prayed, and he did not repeat his ablution.