Thou shalt not take the name of the Lord thy God in vain. It is disputed whether this is a right rendering. Shav in Hebrew means both "vanity" and,'falsehood;" so that the Third Commandment may forbid either "vain-swearing" or simply "false-swearing.
It is in favor of the latter interpretation, that our Lord seems to contrast his own prohibition of unnecessary oaths with the ancient prohibition of false oaths in the words—"Ye have heard that it hath been said by" (or "to") "them of old time—Thou shalt not forswear thyself, but shelf perform unto the Lord thine oaths.
But I say unto you—Swear not at all" (Matthew 5:33-34). It is also in favour of the command being levelled against false-swearing, that perjury should naturally, as a great sin, have a special prohibition directed against it in the Decalogue, while vain-swearing, as a little sin, would scarcely seem entitled to such notice.
Perjury has always been felt to be one of the greatest both of moral and of social offences. It implies an absolute want of any reverence at all for God; and it destroys civil society by rendering the administration of justice impossible.
There has been a general horror of it among all civilised nations. The Egyptians punished perjury with death. The Greeks thought that a divine Nemesis pursued the perjured man, and brought destruction both upon himself and upon his offspring (Herod.
6.86). The Romans regarded the perjurer as infamous, and the object of Divine vengeance in the other world (Cic. De Leg. 2.9). The threat contained in the words—"The Lord will not hold him guiltless"—may be taken as an argument on either side.
If viewed as equivalent to "the Lord will punish severely" (Kalisch), it accords best with the view that perjury was intended; if taken literally, it would suit best a lesser sin, of which men ordinarily think little.