Musnad Abu Ya'la al-Mawsili 152:117

Abu Khaythama narrated to us, Jarir narrated to us, from Layth, from Muhammad ibn Abd al-Rahman ibn Yazid, from his father, who said: I was with Abdullah until he reached the Jamrat al-Aqaba, and I preceded him. He said, "Hand me some stones." So I handed him seven stones while he was reciting the Talbiyah. Then he said, "Take the rein of the she-camel." He came to the bottom of the valley, then turned toward the tree, then said, "Allahu Akbar," and threw. He began to say "Allahu Akbar" at every pebble until he had thrown seven pebbles. Then he said, "O Allah, make it an accepted Hajj and a forgiven sin." Then he said, "This is how he did it, the one upon whom Surah al-Baqarah was revealed."