Musnad Ahmad 482:153

Yahya ibn Ishaq narrated to us, Ibn Lahi'ah informed us, from Yazid, from Abu al-Khayr, from Uqbah ibn Amir, who said: I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying upon the pulpit: "Recite these two verses which are from the end of Surat al-Baqarah, for my Lord gave them—or gave them to me—from beneath the Throne."