Musannaf Ibn Abi Shayba 3:4050

Mulaazim ibn 'Amr narrated to us, from Bishr ibn Farrukh, he said: Ayyub ibn 'Utbah narrated to me, from Yahya ibn Abi Kathir, he said: Whoever comes to the mosque and the prayer has been established, let him delay the two rak'ahs before the dawn (Fajr) until he prays them in the forenoon (Duha).