Musnad Abu Ya'la al-Mawsili 218:7

Muhammad ibn Abdullah ibn Numayr narrated to us, Yunus ibn Bukayr narrated to us, Ibrahim ibn Isma'il informed us, he said: Uthman ibn Ka'b narrated to me, he said: Rabi', a man from Banu al-Nadir who was under the guardianship of Safiyyah, narrated to me, from Safiyyah bint Huyayy, she said: I have never seen anyone better in character than the Messenger of Allah, may Allah bless him and grant him peace. I saw him when he mounted me behind him on his she-camel from Khaybar at night. I began to doze off, and my head would strike the back of the saddle, so he would touch me with his hand and say, "O you, gently, O daughter of Huyayy." Until, when he reached al-Sahba', he said, "Indeed, I apologize to you, O Safiyyah, for what I did to your people, for they said to me such and such."