Deuteronomy 13:9

9 You must certainly put them to death. Your hand must be the first in putting them to death, and then the hands of all the people.

Read Deuteronomy 13:9 Using Other Translations

But thou shalt surely kill him; thine hand shall be first upon him to put him to death, and afterwards the hand of all the people.
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.
You must put them to death! Strike the first blow yourself, and then all the people must join in.