Musnad Ahmad 790:149

Yazid narrated to us, he said: Hisham informed us; and Rawh said: Hisham narrated to us, from al-Hasan, from ‘Imran ibn Husayn, who said: We traveled by night with the Messenger of Allah (may Allah bless him and grant him peace). When it was the end of the night, we halted to rest, and we did not wake up until the heat of the sun awakened us. One of us began to stand up in a state of alarm to perform his ablution. He said: The Prophet (may Allah bless him and grant him peace) commanded them to be calm. Then we departed and traveled until the sun had risen, then he performed ablution. Then he commanded Bilal, so he gave the adhan, then he prayed the two rak'ahs before the dawn prayer. Then he gave the iqamah, and we prayed. They said: "O Messenger of Allah, should we not repeat it at its [proper] time tomorrow?" He said: "Does your Lord forbid you from usury (riba) and then accept it from you?"