Exodus 32:28-30

Amplified Bible

²⁸ So the sons of Levi did as Moses instructed, and about three thousand men of the people [of Israel] were killed that day. ²⁹ Then Moses said [to the Levites], “Dedicate yourselves today to the Lord—for each man has been against his own son and his own brother [in his attempt to escape execution]—so that He may restore and bestow His blessing on you this day.”

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