The Levites did as Moses commanded, and that day about three thousand of the people fell dead.
Moses begins with Aaron, not ordering his death like the ringleaders, because there is a world of difference between those who rush headlong into sin and those surprised by infirmity into it. Aaron deserved to be cut off, and would have been, except Moses interceded for him; now he calls him to repentance, showing him he hardened their hearts and strengthened their hands in idolatry.
AI summary
Commenting on Exodus 32:21-29
The Levites consecrated themselves to the Lord by obeying Moses, sparing no relation found in this idolatry, just as Aaron and his sons were consecrated by sacrifice. God blessed them that day by taking them into His service to minister in the sanctuary and bear His vessels, with the tithes of the people for their maintenance.
AI summary
The three thousand slain were the chief transgressors who broke the covenant by taking other gods. Having lost Divine protection through their apostasy, the justice of God laid hold on them; Moses acted under positive orders from God, for though the nation was spared from extermination through his intercession, those set on mischief had to die.
AI summary