Exodus 20:7

Thou shalt not take the name of the Lord thy God in vain. — The Hebrew is ambiguous, as is to some extent the English translation. Most modern critics regard the phrase used as forbidding false swearing only; but some think that it forbids also “profane” or “vain swearing.” Our Lord’s comment in the Sermon on the Mount favours the view that false swearing alone was actually forbidden by the Law, since He proceeds to condemn profane swearing on His own authority: “But I say unto you” (Matthew 5:34). False swearing is among the greatest insults that man can offer to God, and, as being such, is naturally forbidden in the first table, which teaches us our duty to God. It is also destructive of civil society; and hence it is again forbidden in the second table (Exodus 20:16), which defines our duties to our neighbour. The laws of all organised States necessarily forbid it, and generally under a very severe penalty. The Jewish Law condemned the false witness to suffer the punishment which his evidence was calculated to inflict (Deuteronomy 19:19). The Egyptians visited perjury with death or mutilation. The Greeks were content to punish it with a heavy fine, and ultimately with the loss of civil rights. The Romans, in the more ancient times, inflicted the death penalty. It was generally believed, alike in Egypt, in Greece, and in Rome, that the anger of the gods was especially provoked by this crime, and that a Divine Nemesis pursued those who committed it, and made them suffer for their sin, either in their own person or in that of their posterity.

The Lord will not hold him guiltless. — Punishment will assuredly overtake the perjured man, if not in this life, then in another. Jehovah will vindicate His own honour.