Musnad Ahmad 1153:842

Ibrahim ibn Ishaq and Ali narrated to us, they said: Ibn al-Mubarak narrated to us. Ali said: Ibn al-Mubarak informed us, from Yunus. Ali said: Yunus informed us, from al-Zuhri, he said: Urwah informed me, from Aisha, she said: "When the Messenger of Allah, may Allah bless him and grant him peace, intended to go on a journey, he would cast lots among his wives. Whichever of them her lot came out for, he would take her out with him. He used to divide for each woman among them her day and her night, except that Sawdah bint Zam'ah had gifted her day and her night to Aisha, the wife of the Prophet, may Allah bless him and grant him peace, seeking by that the pleasure of the Prophet, may Allah bless him and grant him peace."