Musannaf Ibn Abi Shayba 16:211

Abu Bakr narrated to us, he said: Ibn 'Uyaynah narrated to us, from al-Walid ibn Kathir, from Wahb ibn Kaysan, that he heard it from 'Umar ibn Abi Salamah, who said: I was a boy under the care of the Prophet, may Allah bless him and grant him peace, and my hand used to wander about in the dish. So he said to me: "O boy, mention the name of Allah, eat with your right hand, and eat from what is in front of you."