Musnad Ahmad 32:2165

Ali ibn Abdullah narrated to us, Mu’adh ibn Hisham narrated to us, he said: My father narrated to me, from Qatadah, Anas ibn Malik narrated to us: "The Prophet, may Allah bless him and grant him peace, used to go around to his wives in one hour of the night and the day, and they were eleven." He said: I said to Anas: "Was he capable of that?" He said: "We used to say that he was given the strength of thirty."