John Gill Commentary 1 Corinthians 7:37

"But he that standeth stedfast in his heart, having no necessity, but hath power as touching in his own heart, to keep his own virgin [daughter], shall do well." — 1 Corinthians 7:37 (ASV)

Nevertheless, he that stands steadfast in his heart
The apostle returns to confirm his former advice, where it can be attended to with safety; and observes, that notwithstanding what he has allowed might lawfully be done, and was proper to be done; yet a man that had deliberated upon, and had well weighed the matter of virginity, the case of a single life, and was at a point about in, having no hesitation nor fluctuation of mind concerning it: and also "having no necessity"; of acting otherwise, either through the meanness of his circumstances, or rather through the weakness of his virgin, she not having the gift of continency:

but has power over his own will ;
his daughter's will being the same with his, and she entirely consenting to live a single life; otherwise he would have no power of acting as he pleased in such a case:

and has so decreed in his heart :
it is a fixed point on mature deliberation, in which he himself is hearty and determined, and his child perfectly assents to it, so that on all hands it is an agreed matter:

that he will keep his virgin ;
at home with him, unmarried, and not give her to any man in marriage:

does well :
or that which is for both temporal and spiritual profit and advantage, as before observed. Some understand all this of a man's keeping his own virginity, and determining to continue unmarried.