Passage Deuteronomy 13:8
Deuteronomy 13:6-10 deals with a person who secretly urges others to serve other gods, even a close relative or friend. In the verses that follow, the hearer must show no pity, must not spare or conceal the person, and must strike the first blow.
The passage is a plain command with a plain penalty. The critical question is how it was meant to work as law in ancient Israel, and how later readers, Jewish and Christian, have treated it.
you shall not yield to him or listen to him, nor shall your eye pity him, nor shall you spare him, nor shall you conceal him.
Deuteronomy 13:8
But you shall kill him. Your hand shall be first against him to put him to death, and afterward the hand of all the people.
Deuteronomy 13:9
Source: see Credits and references (no. 5, p. 6).