Musnad Ahmad 26:716

I read to my father: Ali narrated to us, from al-Hajari, from Abu al-Ahwas, from Abdullah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "When the servant of one of you brings his food to him, let him seat him with him, or let him give him a portion of it, for he is the one who took care of its heat and its smoke."