Musnad Abu Ya'la al-Mawsili 17:1

Abu Bakr ibn Abi Shaybah and Abu Kurayb narrated to us, they said: Zayd ibn al-Hubab narrated to us, from Musa ibn Ubaydah, from Ubayd ibn Salman al-Qurashi, from Ata ibn Yasar, from Jahjah al-Ghifari, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "The believer eats in one intestine, and the disbeliever eats in seven intestines."