Nevertheless, to avoid fornication, let every man have his own wife, and let every woman have her own husband. To avoid fornication - Δια τας πορνειας· verto, propter exercendam libidinem, vel ut libidinem licite exercere liceat. Probo hanc notionem ex Hebraeo, ibi זנה, zanah, est libidinem exercere, Hosea 4:10 : For they shall eat and not have enough; they shall commit whoredom, תזנו, libidinem exercebunt, and shall not increase. Here the prophet certainly does not speak of whoredom in our sense of the word; for the persons he mentions expected to have children, which cannot be said of those who are addicted to improper connections: the prophet speaks concerning married persons, whom he threatens with a privation of children, notwithstanding libidinem exercebant in order to have numerous families. See Schoettgen. The following verse shows that this is the apostle's meaning.
Let every man have his own wife - Let every man have one woman, his own; and every woman one man, her own. Here, plurality of wives and husbands is most strictly forbidden; and they are commanded to marry for the purpose of procreating children.
In the Jewish constitutions there are some things not only curious, but useful, respecting marriage. "There are four causes which induce men to marry:
1. Impure desire;
2. To get riches;
3. To become honorable;
4. For the glory of God.
Those who marry through the first motive beget wicked and rebellious children. Those who marry for the sake of riches have the curse of leaving them to others. Those who marry for the sake of aggrandizing their family, their families shall be diminished. Those who marry to promote the glory of God, their children shall be holy, and by them shall the true Church be increased."