Musnad Ahmad 30:2146

'Affan narrated to us, he said: Hammad narrated to us, he said: 'Ammar ibn Abi 'Ammar informed us, he said: I heard Abu Hurairah say: The Messenger of Allah (peace and blessings of Allah be upon him) said: "When the servant of one of you brings his food, having been spared its heat and its labor, if he does not seat him with him to eat, then let him hand him a morsel of his food."