John Calvin Commentary Exodus 32:8

"they have turned aside quickly out of the way which I commanded them: they have made them a molten calf, and have worshipped it, and have sacrificed unto it, and said, These are thy gods, O Israel, which brought thee up out of the land of Egypt." — Exodus 32:8 (ASV)

They have turned aside quickly out of the way. So swift a transgression, as I have said, aggravates their crime. God then states the nature of their corruption: that they have worshipped a molten calf, that is, the work of their own hands.

But it should be observed that what they had put forward as a pretext for their ungodliness is mentioned last, as the climax of their sin. For when they said, These were their gods which had brought them up, their aim was to offer a legitimate excuse. They presented it as if they were not falling away from the worship of the true God, their Deliverer. Instead, they claimed it was evidence of their more fervent zeal that they should fall down as worshippers before the calf in His honor.

But God refutes this and complains of the gross indignity done to Him when a dead image of a calf was substituted for His glory.