Deuteronomy 17:5-7

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

6The one condemned to die is to be executed on the testimony of two or three witnesses. No one is to be executed on the testimony of a single witness.

7The witnesses’ hands are to be the first in putting him to death, and after that, the hands of all the people. You must purge the evil from you.