What does Exodus 32:27 mean?

He told them, 'This is what the Lord, Israel’s God, says: Each of you, strap on your sword. Go through the camp from one end to the other. Kill your brother, your friend, your neighbor.' Exodus 32:27 - Modern Text Bible

(Moses relays a harsh command from God: the Levites must punish the idolaters, even if it means killing people close to them. This is about purging the community of rebellion.)