John Gill Commentary 1 Corinthians 7:4

"The wife hath not power over her own body, but the husband: and likewise also the husband hath not power over his own body, but the wife." — 1 Corinthians 7:4 (ASV)

The wife has not power of her own body
To refrain the use of it from her husband; or to prostitute it to another man:

but the husband ;
he has the sole power over it, and may require when he pleases the use of it:

and likewise also the husband has not power over his own body :
to withhold due benevolence, or the conjugal debt from his wife; or abuse it by self-pollution, fornication, adultery, sodomy, or any acts of uncleanness: but the wife; she only has a power over it, a right to it, and may claim the use of it:

this power over each other's bodies is not such, as that they may, by consent, either the husband allow the wife, or the wife the husband, to lie with another.