Narrated Nafi`: Ibn `Umar never used to take his meal unless a poor man was called to eat with him. One day I brought a poor man to eat with him, the man ate too much, whereupon Ibn `Umar said, "O Nafi`! Don't let this man enter my house, for I heard the Prophet (ﷺ) saying, "A believer eats in one intestine (is satisfied with a little food), and a kafir (unbeliever) eats in seven intestines (eats much food).
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا مُحَمَّدُ بْنُ بَشَّارٍ، حَدَّثَنَا عَبْدُ الصَّمَدِ، حَدَّثَنَا شُعْبَةُ، عَنْ وَاقِدِ بْنِ مُحَمَّدٍ، عَنْ نَافِعٍ، قَالَ كَانَ ابْنُ عُمَرَ لاَ يَأْكُلُ حَتَّى يُؤْتَى بِمِسْكِينٍ يَأْكُلُ مَعَهُ، فَأَدْخَلْتُ رَجُلاً يَأْكُلُ مَعَهُ فَأَكَلَ كَثِيرًا فَقَالَ يَا نَافِعُ لاَ تُدْخِلْ هَذَا عَلَىَّ سَمِعْتُ النَّبِيَّ صلى الله عليه وسلم يَقُولُ " الْمُؤْمِنُ يَأْكُلُ فِي مِعًى وَاحِدٍ وَالْكَافِرُ يَأْكُلُ فِي سَبْعَةِ أَمْعَاءٍ ".
sunnah.com