Exodus 32:28

25 And Moses saw that the people were out of control, for Aaron had let them loose to their shame before their haters:

26 Then Moses took his place at the way into the tents, and said, Whoever is on the Lord's side, let him come to me. And all the sons of Levi came together to him.

27 And he said to them, This is the word of the Lord, the God of Israel: Let every man take his sword at his side, and go from one end of the tents to the other, putting to death his brother and his friend and his neighbour.

28 And the sons of Levi did as Moses said; and about three thousand of the people were put to death that day.

29 And Moses said, You have made yourselves priests to the Lord this day; for every one of you has made the offering of his son and his brother; the blessing of the Lord is on you this day.

30 And on the day after, Moses said to the people, Great has been your sin: but I will go up to the Lord, and see if I may get forgiveness for your sin.

31 Then Moses went back to the Lord and said, This people has done a great sin, making themselves a god of gold;