Exodus 32:25-29

25Moses saw that the people were out of control, for Aaron had let them run wild and become a laughingstock1 to their enemies. 26So Moses stood at the entrance to the camp and said, “Whoever is for the LORD, come to me.”

And all the Levites gathered around him.

27He told them, “This is what the LORD, the God of Israel, says: ‘Each of you men is to fasten his sword to his side, go back and forth through the camp from gate to gate, and slay his brother, his friend, and his neighbor.’”

28The Levites did as Moses commanded, and that day about three thousand of the people fell dead.

29Afterward, Moses said, “Today you have been ordained2 for service to the LORD, since each man went against his son and his brother; so the LORD has bestowed a blessing on you this day.”