Sahih Bukhari: Hadith 269

Anas bin Malik said, "The Prophet (ﷺ) used to visit all his wives in a round, during the day and night and they were eleven in number." I asked Anas, "Had the Prophet (ﷺ) the strength for it?" Anas replied, "We used to say that the Prophet (ﷺ) was given the strength of thirty (men)." And Sa`id said on the authority of Qatada that Anas had told him about nine wives only (not eleven).