John Calvin Commentary Exodus 32:35

"And Jehovah smote the people, because they made the calf, which Aaron made." — Exodus 32:35 (ASV)

And the Lord plagued the people. Moses here briefly attributes to God what he had before related concerning the slaughter of the three thousand, lest anyone think that he had struck them with excessive severity. Therefore, Paul instructs us to consider in this history, as in a mirror, how greatly displeasing idolatry is to God, lest we imitate those who were struck by His hand (1 Corinthians 10:7).

The indignation of Moses is consequently connected with the command of God. Meanwhile, he commends the mercy of God in having spared Aaron, while he speaks of the calf as his work, as well as that of all the people; in a different way indeed, for Aaron formed the calf at their request; still the guilt was common to them.