Musannaf Ibn Abi Shayba 3:3964

Azhar narrated to us, from Ibn 'Awn, who said: Abdullah narrated to me, from Muhammad ibn Sirin, that he used to recite in the two rak'ahs before the dawn (prayer): "Say, 'O disbelievers,'" and "Say, 'He is Allah, [who is] One.'"