Mishkat al-Masabih 21 Foods كتاب الأطعمة 92

وَعَنْ جَعْفَرِ بْنِ مُحَمَّدٍ عَنْ أَبِيهِ قَالَ: كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ إِذَا أَكَلَ مَعَ قَوْمٍ كَانَ آخِرَهُمْ أَكْلًا. رَوَاهُ الْبَيْهَقِيّ فِي «شعب الْإِيمَان» مُرْسلا

Ja’far b. Muhammad told on his father’s authority that when God’s messenger ate along with people he was the last to finish eating. Baihaqi transmitted it in Shu’ab al-iman in mursal form.