Musannaf Ibn Abi Shayba 3:2513

Waki’ narrated to us, from Sufyan, from Sa’d ibn Ibrahim, from ‘Ata’ ibn Yasar, who said: The Messenger of Allah (may Allah bless him and grant him peace) prayed the two rak’ahs of Fajr after he had passed the valley. Then he commanded Bilal, so he gave the adhan, then he gave the iqamah, then he prayed the obligatory prayer.