Musnad Ahmad 25:1578

Ibn Fudayl narrated to us, Rashdin ibn Kurayb informed us, from his father, from Ibn Abbas, who said: "I prayed with the Prophet, peace and blessings of Allah be upon him, and I stood beside him on his left. So he took hold of me and placed me on his right." He said: And Ibn Abbas said: "And I was on that day ten years old."