John Calvin on 1 Corinthians 7:2

2. But to avoid fornication He now commands, that those who are liable to the vice of incontinency should have recourse to the remedy. For though it may seem that the statement is universal, it ought, nevertheless, to be restricted to those who feel themselves urged by necessity. As to this, every one must judge for himself. Whatever difficulty, therefore, is perceived to be in marriage, let all that cannot resist the promptings of their flesh, know that this commandment has been enjoined upon them by the Lord. But it is asked — “Is this the only reason for entering into matrimony, that we may cure incontinency?” I answer, that this is not Paul’s meaning; for as for those that have the gift of abstinence from marriage, he leaves them at liberty, “Il laisse la liberte de se marier ou ne se marier point;” — “He gives liberty to marry or not marry.” while he commands others to provide against their infirmity by marrying. The sum is this — that the question is not as to the reasons for which marriage has been instituted, but as to the persons for whom it is necessary. For if we look to the first institution, it could not be a remedy for a disease which had as yet no existence, but was appointed for begetting offspring; but after the fall, this second purpose was added.

This passage is also opposed to (τολυγαμία) polygamy For the Apostle desires that every woman have her own husband, intimating that the obligation is mutual. The man, therefore, who has once pledged his fidelity to a woman as his wife, must not separate from her, as is manifestly done in case of a second connection.

1 Corinthians 7:3-5

3. Let the husband render unto the wife due benevolence: and like also the wife unto the husband.

3. Uxori vir debitam benevolentiam vicissim praetet, similiter et uxor marito.

4. The wife hath not power of her own body, but the husband: and likewise also the husband hath not power of his own body, but the wife.

4. Mulier corporis sui potestatem non habet, sed maritus: similiter et maritus corporis sui potestatem non habet, sed uxor.

5. Defraud ye not one the other, except it be with consent for a time, that ye may give yourselves to fasting and prayer; and come together again, that Satan tempt you not for your incontinency.

5. Ne fraudetis alter alterum, nisi ex mutuo consensu ad tempus, ut vacetis ieiunio et orationi: et rursum in unum redite, ne tentet vos Satanas propter incontinentiam vestram.