Musnad Ahmad 30:2746

Muhammad ibn Ja’far and Bahz narrated to us, they said: Shu’bah narrated to us, from ‘Adi ibn Thabit—Bahz said in his narration: He said: ‘Adi ibn Thabit informed me, he said: I heard Abu Hazim—the meaning—narrating from Abu Hurairah, that a man came to the Prophet, may Allah bless him and grant him peace, while he was a disbeliever, and he used to eat a great deal of food. Then he embraced Islam, and he began to eat a little food. That was mentioned to the Prophet, may Allah bless him and grant him peace, so he said: "Indeed, the disbeliever eats in seven intestines, and the Muslim eats in one intestine."