Deuteronomy 20:13

13 When the LORD your God delivers it into your hand, put to the sword all the men in it.

Read Deuteronomy 20:13 Using Other Translations

And when the LORD thy God hath delivered it into thine hands, thou shalt smite every male thereof with the edge of the sword:
And when the LORD your God gives it into your hand, you shall put all its males to the sword,
When the LORD your God hands the town over to you, use your swords to kill every man in the town.