Deuteronomy 17:5-7

5you must punish that person. Take the man or woman who has done that wicked thing to the gate of the town. Then you must throw stones at that person to kill them.

6But two or three people must agree about what the person has done. You must never kill anyone because of the words of only one person.

7The people who saw the wicked act must throw the first stones to kill the person. Then everyone else must also throw stones. In that way, you must remove evil acts from among you.