Deuteronomy 17:4 (KJV)

If there be found among you, within any of thy gates which the Lord thy God giveth thee, man or woman, that hath wrought wickedness in the sight of the Lord thy God, in transgressing his covenant,

And hath gone and served other gods, and worshipped them, either the sun, or moon, or any of the host of heaven, which I have not commanded;

And it be told thee, and thou hast heard of it, and enquired diligently, and, behold, it be true, and the thing certain, that such abomination is wrought in Israel:

Then shalt thou bring forth that man or that woman, which have committed that wicked thing, unto thy gates, even that man or that woman, and shalt stone them with stones, till they die.

At the mouth of two witnesses, or three witnesses, shall he that is worthy of death be put to death; but at the mouth of one witness he shall not be put to death.