Musannaf Ibn Abi Shayba 16:319

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: Al-A’mash narrated to us, he said: I think Abu Khalid al-Walibi mentioned it from Maymunah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The disbeliever eats in seven intestines, and the believer eats in one intestine."