It was narrated from Ibn 'Abbas that: a woman came to the Prophet (ﷺ) and became Muslim, and a man married her. Then her first husband came and said: "O Messenger of Allah, I became Muslim with her, and she knew that I was Muslim." So the Messenger of Allah (ﷺ) took her away from her second husband and returned her to her first husband.
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا أَحْمَدُ بْنُ عَبْدَةَ، حَدَّثَنَا حَفْصُ بْنُ جُمَيْعٍ، حَدَّثَنَا سِمَاكٌ، عَنْ عِكْرِمَةَ، عَنِ ابْنِ عَبَّاسٍ، أَنَّ امْرَأَةً، جَاءَتْ إِلَى النَّبِيِّ ـ صلى الله عليه وسلم ـ فَأَسْلَمَتْ . فَتَزَوَّجَهَا رَجُلٌ . قَالَ فَجَاءَ زَوْجُهَا الأَوَّلُ فَقَالَ يَا رَسُولَ اللَّهِ إِنِّي قَدْ كُنْتُ أَسْلَمْتُ مَعَهَا وَعَلِمَتْ بِإِسْلاَمِي . قَالَ فَانْتَزَعَهَا رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ مِنْ زَوْجِهَا الآخَرِ وَرَدَّهَا إِلَى زَوْجِهَا الأَوَّلِ .
sunnah.com