Deuteronomy 17:2

17:2 Suppose a man or woman is discovered among you – in one of your villages that the Lord your God is giving you – who sins before the Lord your God and breaks his covenant

Deuteronomy 17:6-7

17:6 At the testimony of two or three witnesses they must be executed. They cannot be put to death on the testimony of only one witness. 17:7 The witnesses must be first to begin the execution, and then all the people are to join in afterward. In this way you will purge evil from among you.