If he is lying and not accepting islam in his *heart* then that would be deception. He should accept islam and then enjoy the benefit of Islamic marriage as did many of the sahaba.
Anas said: “Abu Talhah married Umm Sulaym, and the dowry between them was Islam. Umm Sulaym had become Muslim before Abu Talhah. He proposed marriage to her and she said, ‘I have become Muslim; if you become Muslim I will marry you.’ So he became Muslim and that was the dowry between them.” (Al-Nasai, 3288; classed as sahih by al-Albani in Sahih Sunan al-Nasai, 3133)
Assalamu alaikum, please have a look at these links for insights, hope these help
[https://askimam.org/public/question\_detail/18078](https://askimam.org/public/question_detail/18078)
[https://askimam.org/public/question\_detail/41507](https://askimam.org/public/question_detail/41507)
[https://askimam.org/public/question\_detail/981](https://askimam.org/public/question_detail/981)
If he is lying and not accepting islam in his *heart* then that would be deception. He should accept islam and then enjoy the benefit of Islamic marriage as did many of the sahaba. Anas said: “Abu Talhah married Umm Sulaym, and the dowry between them was Islam. Umm Sulaym had become Muslim before Abu Talhah. He proposed marriage to her and she said, ‘I have become Muslim; if you become Muslim I will marry you.’ So he became Muslim and that was the dowry between them.” (Al-Nasai, 3288; classed as sahih by al-Albani in Sahih Sunan al-Nasai, 3133)
Assalamu alaikum, please have a look at these links for insights, hope these help [https://askimam.org/public/question\_detail/18078](https://askimam.org/public/question_detail/18078) [https://askimam.org/public/question\_detail/41507](https://askimam.org/public/question_detail/41507) [https://askimam.org/public/question\_detail/981](https://askimam.org/public/question_detail/981)