Deuteronomy 17:6
At the mouth of two witnesses, or three witnesses, he who is to die shall be put to death. At the mouth of one witness he shall not be put to death.
World English Bible (Public Domain)
In context
Before · Deuteronomy 17:4–5
4and you are told, and you have heard of it, then you shall inquire diligently. Behold, if it is true, and the thing certain, that such abomination is done in Israel, 5then you shall bring out that man or that woman who has done this evil thing to your gates, even that same man or woman; and you shall stone them to death with stones.
6At the mouth of two witnesses, or three witnesses, he who is to die shall be put to death. At the mouth of one witness he shall not be put to death.
After · Deuteronomy 17:7–8
7The hands of the witnesses shall be first on him to put him to death, and afterward the hands of all the people. So you shall remove the evil from among you. 8If there arises a matter too hard for you in judgment, between blood and blood, between plea and plea, and between stroke and stroke, being matters of controversy within your gates, then you shall arise, and go up to the place which the LORD your God chooses.