LIMITS ON PROPHET MUHAMMAD’S WIVES
Muslims were not allowed to marry any of the wives of Prophet Muhammad after he passed away because they were like their mothers.
In the Quran, God described the wives of the Prophet as being unlike other women (they should be seen by other Muslims as exemplary and as the mothers of believers).
If any of the Prophet’s wives committed a manifestly sinful deed, the punishment would be doubled for her. But if any of the Prophet’s wives devoutly obeyed God and His Messenger and performed righteous deeds, she would receive double rewards.
Muhammad’s wives had freedom of choice: God asked Muhammad (as indicated in the Quran, chapter 33 verses 28,29) to give his wives two options, either be released (i.e. divorced) if any of them desired the world’s life and its adornment, or stay married to Prophet Muhammad and devote their lives fully for the cause of Islam.
All of them chose the second option and all of them stayed married to Prophet Muhammad. After Muhammad passed away, none of them remarried.