Musnad Ahmad 33:730

Muhammad ibn Humayd Abu Sufyan—meaning al-Ma'mari—narrated to us, from Sufyan, and Abu Ahmad narrated to us, from Sufyan, from Abu al-Zubayr, from Jabir, that the Messenger of Allah, peace and blessings of Allah be upon him, said: "Indeed, the disbeliever eats in seven intestines, and the believer eats in one intestine."