Exodus 32:25-29

25Now when Moses saw that the people were 1out of control--for Aaron had 2let them 3get out of control to the point of being an object of ridicule among 4their enemies-- 26Moses then stood at the gate of the camp, and said, “Whoever is for the Lord, come to me!” And all the sons of Levi gathered together to him. 27And he said to them, “This is what the Lord, the God of Israel says: ‘Every man of you put his sword on his thigh, and go back and forth from gate to gate in the camp, and kill every man his brother, and every man his friend, and every man his 5neighbor.’” 28So 6the sons of Levi did 7as Moses instructed, and about three thousand men of the people fell that day. 29Then Moses said, “8Dedicate yourselves today to the Lord--for every man has been against his son and against his brother--in order that He may bestow a blessing upon you today.”