Deuteronomy 20:13 Midrash

וּנְתָנָ֛הּ יְהוָ֥ה אֱלֹהֶ֖יךָ בְּיָדֶ֑ךָ וְהִכִּיתָ֥ אֶת־כָּל־זְכוּרָ֖הּ לְפִי־חָֽרֶב׃

And when the LORD thy God delivereth it into thy hand, thou shalt smite every male thereof with the edge of the sword;