Musnad Ahmad 1302:21

Waki’ narrated to us, Sufyan and ‘Abd al-Rahman narrated to us, from Sufyan, from Abu Ishaq, from Abu Habibah al-Ta’i, from Abu al-Darda’—‘Abd al-Rahman said in his narration: "So I met Abu al-Darda’"—who said: I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "The likeness of the one who emancipates [a slave] at the time of death is like the likeness of the one who gives a gift when he is full."