Aishah (may Allah be pleased with her) said: After this verse was revealed, "You may defer whom you will of them and take to yourself whom you will" [Surah al-Ahzab: 51], the Messenger of Allah (peace and blessings be upon him) used to ask our permission on the day (turn) of any one of us. Mu'adhah said: Then what did you say to the Messenger of Allah (peace and blessings be upon him) when he (peace and blessings be upon him) asked your permission? Aishah (may Allah be pleased with her) said: I would say: If that were up to me, I would not prefer anyone over myself.
Imam al-Shafi'i (may Allah have mercy on him) said: And when he (peace and blessings be upon him) intended to travel, he would cast lots among them, and whichever of them drew the lot, he would take her with him.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13431