Exodus 32:28-30

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

29Then Moses said, “You have been set apart to the LORD today, for you were against your own sons and brothers, and he has blessed you this day.”

30The next day Moses said to the people, “You have committed a great sin. But now I will go up to the LORD ; perhaps I can make atonement for your sin.”