John Calvin Commentary Exodus 20:14

"Thou shalt not commit adultery." — Exodus 20:14 (ASV)

Although only one kind of impurity is specifically referred to, it is sufficiently clear from the principle laid down that believers are generally exhorted to chastity. For if the Law is a perfect rule of holy living, it would be more than absurd to grant a license for fornication, with only adultery being excepted.

Furthermore, it is incontrovertible that God will by no means approve or excuse before His tribunal what the common sense of mankind declares to be obscene. Although lewdness has been rampant everywhere in every age, the conviction that fornication is a scandal and a sin could never be utterly extinguished.

Unquestionably, what Paul teaches has been widely accepted from the beginning: that a good life consists of three parts—soberness, righteousness, and godliness (Titus 2:12), and the soberness he commands does not differ from chastity.

Besides, when Christ or the Apostles discuss a perfect life, they always refer believers to the Law. For, as it had been said by Moses long ago, This is the way, walk ye in it;⁵⁹ Christ confirms this:

If thou wilt enter into life, keep the commandments (Matthew 19:17).

And Paul corroborates it: He that loveth another hath fulfilled the Law (Romans 13:8), while they constantly pronounce a curse against all fornicators. It is not worthwhile to quote the particular passages in which they do so.

Now, if Christ and the Apostles, who are the best interpreters of the Law, declare that God’s Law is violated as much by fornication as by theft, we certainly infer that in this Commandment the whole genus is comprehended under a single species.

Therefore, those who have sought to be praised for their acuteness on account of their ridiculous subtlety—admitting that fornication is indeed condemned with sufficient clarity and frequency in the New Testament, but not in the Law—have done nothing but betray their disgraceful ignorance.

For, if they had reasoned justly, since God is declared to have blessed marriage, it must at once be concluded, on the contrary, that any sexual connection between male and female outside of marriage is accursed. This is the argument of the author of the Epistle to the Hebrews, where he contrasts two opposite things:

Marriage (he says) is honorable in all, and the bed undefiled; but whoremongers and adulterers God will judge (Hebrews 13:4).

So also, when God forbids the priest to marry a harlot (Leviticus 21:14), the manifest impropriety of fornication is declared. And if it was unlawful for the daughters of Israel to be harlots (Deuteronomy 23:17), the same reasoning necessarily applies to males.

From where else did Hosea take that reproof but from the Law? Whoredom and wine take away the heart (Hosea 4:11). Thus, when the Prophets metaphorically condemn the corruptions of their nation, they do not always use the same word as Moses does here, נפ, naaph, but compare them to fornications. If fornication were lawful in itself, this metaphor would be entirely inappropriate.

Hosea was commanded to take a harlot for a wife (Hosea 1:2); no mention is made of adultery, yet the shame and baseness of the people is thus condemned. Who, then, would say that fornication is free from sin, since God brands it with such a significant mark of disgrace?

But if anyone should stubbornly contest this, let him accuse Paul of error, who testifies that an example is set before us in the Law, that we should not commit fornication as some of them committed, and fell in one day three-and-twenty thousand (Numbers 25:9; 1 Corinthians 10:8). Surely, if they had not transgressed the Law, such a horrible vengeance would not have overwhelmed them.

If anyone should object that the crime of idolatry was mixed up with it, still the declaration of Paul remains untouched: that God was the avenger of fornication in this infliction of punishment, which would not be consistent unless fornication were a transgression of the Law.

And in truth, when, as recorded by Luke (Acts 15:20), the Apostles in their decree prohibit fornication among the Gentiles, the reason is at the same time added, that Moses is read in the synagogues. Now, if fornication were not a vice opposed to the Law, no offense would have arisen from this.

We have already explained why, under this word adultery, every impure lust was condemned. We know how unbridled the licentiousness of the Gentiles was; for, although God never allowed all shame to be extinguished along with their purity, still respect for what was right was in a manner stifled, so that they evaded the grossness of the sin by ribaldry and scurrilous jests. At any rate, the doctrine of Paul was by no means understood, that those who indulge in whoredom sin against their own body (1 Corinthians 6:18).

Since, then, the minds of all people were stupefied by indulgence, it was necessary to arouse them by declaring the atrocity of the sin, so that they might learn to beware of all pollution. Nor are unbridled lusts alone condemned here, but God also instructs His people to cherish modesty and chastity. The sum is that those who desire to commend themselves to God should be pure from all filthiness of the flesh and spirit (2 Corinthians 7:1); nor can we doubt that Paul, in these words, intended to interpret the Law, as he elsewhere exhorts:

that everyone should possess his vessel in sanctification and honor; not in the lust of concupiscence, even as the Gentiles which know not God (1 Thessalonians 4:4–5).

⁵⁹ The quotation is not from the writings of Moses, but an accommodation from Isaiah 30:21..