Musnad Ahmad 26:587

'Abd al-Rahman narrated to us, from Sufyan, from al-A'mash, from 'Umarah, from 'Abd al-Rahman ibn Yazid, from 'Abdullah, who said: "I did not see the Messenger of Allah, may Allah bless him and grant him peace, perform any prayer except at its appointed time, except that he combined the Maghrib and the Isha at Jam' (Muzdalifah), and he performed the Subh (Fajr) prayer on that day before its [usual] appointed time."