Deuteronomy 17:3-5

3and has gone to serve other gods by bowing in worship to the sun, moon, or all the stars in the sky  — which I have forbidden  —

4and if you are told or hear about it, then investigate it thoroughly. If the report turns out to be true that this detestable act has been done in Israel,

5you are to bring out to your city gates that man or woman who has done this evil thing and stone them to death.