Ibn Umar would not eat until a poor person was brought to eat with him. I once brought in a man to eat with him, and the man ate a great deal.Ibn Umar said, "Nafi, do not bring this man to me again. I heard the Prophet ﷺ say, 'The believer eats with one stomach, and the disbeliever eats with seven stomachs.'"
كان ابن عمر لا يأكل حتى يؤتى بمسكين يأكل معه، فأدخلت رجلا يأكل معه، فأكل كثيرا، فقال: يا نافع، لا تدخل هذا علي، سمعت النبي ﷺ يقول: المؤمن يأكل في معى واحد، والكافر يأكل في سبعة أمعاء.
Bukhari narrated it in the Book of Foods (5393) and Muslim in the Book of Drinks (2060:183), both via the route of Shubah, from Waqid bin Muhammad bin Zayd, that he heard Nafi say, and he related it. The wording given is that of Bukhari, and the wording of Muslim is similar.