Musannaf Ibn Abi Shayba 3:3305

Waki’ narrated to us, from al-‘Ala’ ibn ‘Abd al-Karim, who said: I heard Abu al-Bakhtari on the day of Eid, and he heard a man saying, "The prayer is before the sermon." He said, "The Sunnah, by the Lord of the Kaaba."