You missed a bit. Here is the whole passage:
Originally Posted by Arroyo_Doble
19 When Moses approached the camp and saw the calf and the dancing, his anger burned and he threw the tablets out of his hands, breaking them to pieces at the foot of the mountain.
20 And he took the calf the people had made and burned it in the fire; then he ground it to powder, scattered it on the water and made the Israelites drink it.
21 He said to Aaron, “What did these people do to you, that you led them into such great sin?”
22 “Do not be angry, my lord,” Aaron answered. “You know how prone these people are to evil.
23 They said to me, ‘Make us gods who will go before us. As for this fellow Moses who brought us up out of Egypt, we don’t know what has happened to him.’
24 So I told them, ‘Whoever has any gold jewelry, take it off.’ Then they gave me the gold, and I threw it into the fire, and out came this calf!”
25 Moses saw that the people were running wild and that Aaron had let them get out of control and so become a laughingstock to their enemies.
26 So he stood at the entrance to the camp and said, “Whoever is for the LORD, come to me.” And all the Levites rallied to him.
27 Then he said to them, “This is what the LORD, the God of Israel, says: ‘Each man strap a sword to his side. Go back and forth through the camp from one end to the other, each killing his brother and friend and neighbor.’”
28 The Levites did as Moses commanded, and that day about three thousand of the people died.
29 Then 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.”
30 The 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.”
Moses was putting down a rebellion. It wasn't simply an indiscriminate slaughter. That doesn't compare with Mohammed's reign of terror against the people of Medina and Mecca.