1 Corinthians 7:4

The wife hath not power of her own body but the husband, She has not power, that is, over those members which distinguish woman from man, in so far as they serve for the conjugal act. Power she has not over them so as to contain at her own will or to have intercourse with another. That power belongs to the husband alone, and that for himself only, not for another. Cf. S. Augustine (contra Julian, lib. v.). The Greek is literally, has no right over her body, whether to contain or to hand it over to another.

Likewise also the husband hath not power of his own body, but the wife. Hence it is clear that, though in the government of the family the wife should be subject and obedient to her husband, yet in the right of exacting and returning the marriage debt she is equal with her husband, has the same right over his body that he has over hers, and this from the marriage contract, in which each has given to the other the same power over the body, and received the same power over the other's body. The husband, therefore, is as much bound to render his wife, as the wife her husband, faithfulness and the marriage debt. This is taught at length in their expositions of this passage by Chrysostom. Theophylact, Œcumenius, Primasius, Anselm, and by S. Jerome (Cit. 32, qu. 2, cap. Apostolus), who says that husband and wife are declared to be equal in rights and duties. " When, therefore," says S. Chrysostom (Hom. 19), " a harlot comes and tempts you, say that your body is not your own but your wife's. Similarly, let the wife say to any one who proposes to rob her of her chastity, 'My body is not mine but my husband's. '"