Musnad Abu Ya'la al-Mawsili 131:6

Abu Bakr ibn Abi Shaybah narrated to us, Ali ibn Mushir narrated to us, from al-Mukhtar ibn Fulful, from Anas, who said: The Messenger of Allah (may Allah bless him and grant him peace) led us in prayer one day. When he finished the prayer, he turned his face toward us and said: "O people, I am your Imam, so do not precede me in bowing, nor in prostration, nor in standing, for I see you from in front of me and from behind me." Then he said: "By the One in Whose hand is my soul, if you saw what I saw, you would laugh little and weep much." They said: "And what did you see, O Messenger of Allah?" He said: "I saw Paradise and the Fire."