"Men are overseers over women, by reason of that wherewith Allah hath made one of them excel over another, and by reason of that which they expend of their substance. Wherefore righteous women are obedient, and are watchers in husbands absence by the aid and protection of Allah. And those wives whose refractoriness ye fear, exhort them, and avoid them in beds, and beat them; but if they obey you, seek not a way against them; verily Allah is ever Lofty, Grand." - Quran 4:34 (read more)

"Narrated Qatada: Anas bin Malik said, "The Prophet 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 the strength for it?" Anas replied, "We used to say that the Prophet 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)." - Sahih Bukhari 1:5:268 (read more)

"In the Two Sahihs, it is recorded that `A'ishah said that when Sawdah bint Zam`ah became old, she forfeited her day to `A'ishah, and the Prophet used to spend Sawdah's night with `A'ishah." - Ibn Kathir