Musnad Ahmad 313:1

Yunus narrated to us, Abu 'Awanah narrated to us, from Simak ibn Harb, from a man from the people of Medina, that he prayed behind the Prophet, peace and blessings of Allah be upon him, and he heard him reciting in the dawn prayer: "Qaf. By the Glorious Qur'an," and "Ya-Sin. By the Wise Qur'an."