Mukhtasar Bukhari

Umm al-Mu’minin Aisha (may Allah be pleased with her) said that whenever the Messenger of Allah (peace and blessings be upon him) intended to travel, he would draw lots among his wives. Whosever name was drawn, he would take her with him. And the Prophet (peace and blessings be upon him) would assign one day and night for each of his wives, except for Sawda bint Zam’a (may Allah be pleased with her), who gave her day and night to Umm al-Mu’minin Aisha (may Allah be pleased with her), seeking thereby the pleasure of the Messenger of Allah (peace and blessings be upon him).