Musnad Ahmad 33:110

Waki' narrated to us, Sufyan narrated to us, and (in another chain) Abd al-Rahman narrated to us, from Sufyan, from Abu al-Zubayr, from Jabir, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The food of one person is sufficient for two, and the food of two people is sufficient for four, and the food of four people is sufficient for eight."