Musnad Ahmad 626:31

Yazid narrated to us, Hisham informed us, from Muhammad, who said: I entered the Jami' Mosque, and 'Amr ibn Wahb al-Thaqafi had entered from the other side, so we met near the middle of the mosque. He initiated the conversation with me—and he loved the good he brought to me—so he initiated the conversation with me and said: We were with al-Mughirah ibn Shu'bah—and what he brought of the hadith increased him in my estimation in terms of truthfulness—he said: We said: "Did any man from this nation lead the Prophet, peace and blessings of Allah be upon him, in prayer other than Abu Bakr al-Siddiq?" He said: "Yes, we were on such-and-such a journey. When it was the time before dawn, the Messenger of Allah, peace and blessings of Allah be upon him, struck the neck of his riding beast and set off, and I followed him. He disappeared from me for a while, then he came and said: 'Do you have a need?' I said: 'I have no need, O Messenger of Allah.' He said: 'Is there any water?' I said: 'Yes.' So I poured it for him, and he washed his hands, then he washed his face. Then he went to uncover his forearms, and he was wearing a Syrian jubbah (outer garment) of his, and it was tight, so he put his hands in and brought them out from under the jubbah, and he washed his face, and washed his forearms, and wiped over his forelock, and wiped over the turban and the two leather socks (khuffayn). Then we caught up with the people, and the prayer had been established, and 'Abd al-Rahman ibn 'Awf was leading them in prayer, and he had already prayed one rak'ah. I went to inform him, but he forbade me. So we prayed what we caught up with, and we completed what we had missed."