(516) بَابُ التَّسْلِيمِ عَلَى مَجْلِسٍ فِيهِ الْمُسْلِمُ وَالْمُشْرِكُ
Usama ibn Zayd related that one day the Prophet, may Allah blesshim and grant him peace, was riding on a donkey on a straw saddle coveredby a blanket from Fadak. Usama ibn Zayd was riding behind him. He was onhis way to visit Sa'd ibn 'Ubada. He passed by a meeting which included'Abdullah ibn Ubayy ibn Salul - before the enemy of Allah had becomeMuslim. The gathering contained a mixture of Muslims, associaters and idolaters.He greeted them.
Reference: Al-Adab Al-Mufrad 1108
In-book reference: Book 44, Hadith 8
English translation: Book 44, Hadith 1108