It was narrated that Ibn 'Abbas (رضي الله عنه) said:

A woman became Muslim at the time of the Messenger of Allah (ﷺ) and got married. Her first husband came to the Prophet (ﷺ) and said: O Messenger of Allah, I had become Muslim and she knew that I was Muslim. So the Prophet (ﷺ) separated her from her second husband and gave her back to her first husband.