It was narrated from Nafi' bin Jubair, from his father, that the Messenger of Allah (ﷺ) said during a journey:
"Who will watch out for dawn for us, so that we do not sleep and miss the dawn prayer?" Bilal said: 'I will.' He turned to face the direction where the sun woke them up, then they got up. He said: 'Perform Wudu'.' Then Bilal called the Adhan and he prayed two Rak'ahs, and they prayed the two (Sunnah) Rak'ahs of Fajr, then they prayed Fajr." (ES)
English reference (ES): Vol. 1, Book 6, Hadith 625 (ES)
Arabic reference (ES): Book 6, Hadith 631 (ES)