Mishkat al-Masabih 21 Foods كتاب الأطعمة 16

وَعَنْهُ قَالَ قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «طَعَامُ الِاثْنَيْنِ كَافِي الثلاثةِ وطعامِ الثلاثةِ كَافِي الْأَرْبَعَة»

He reported God’s messenger as saying, “Two people’s food is enough for three and three people’s is enough for four.” (Bukhari and Muslim.)