John Gill Commentary 1 Corinthians 7:13

"And the woman that hath an unbelieving husband, and he is content to dwell with her, let her not leave her husband." — 1 Corinthians 7:13 (ASV)

And the woman which has an husband that believeth
The apostle puts the case both ways, there being the same reason for one as for another; that if she that was a sister, who was partaker of the grace of God, and a member of the church, had a husband to whom she was married before her conversion; who was an unbeliever, had no faith in Christ, nor any notion of the Gospel, but an infidel to both:

and if he be pleased to dwell with her ;
loves her, and is willing to continue with her; neither puts her away from him, nor departs from her on account of her Christianity:

let her not leave him ;
but continue, and cohabit with him as man and wife; this is the advice the apostle gives, as agreeably to the light of nature and reason; as becoming the Gospel of Christ, and as what might serve to recommend it, and spread the knowledge of it.