Musnad Ahmad 30:396

'Abd al-A'la narrated to us, from Ma'mar, from al-Zuhri, from Abu Salamah, from Abu Hurayrah, that the Messenger of Allah (may Allah bless him and grant him peace) said: "When the servant of one of you prepares his food for him, and he has spared him its heat and its smoke, let him have him sit with him. If he refuses, then let him hand him a morsel in his hand."