Musnad Ahmad 30:2430

Yahya narrated to us, from Shu'bah, who said: Muhammad ibn Ziyad narrated to us, from Abu Hurairah; and Muhammad ibn Ja'far said: Shu'bah narrated to us, from Muhammad ibn Ziyad, who said: I heard Abu Hurairah, from the Prophet, peace and blessings of Allah be upon him, saying: "When the servant of one of you brings his food, let him seat him with him. If he does not seat him with him, then let him hand him a morsel or two, or a bite or two — and Ibn Ja'far said: a morsel or two — for he is the one who took charge of its preparation and its heat."