John Calvin Commentary Leviticus 20:1

"And Jehovah spake unto Moses, saying," — Leviticus 20:1 (ASV)

And the Lord spoke. The prohibition of this superstition was previously explained in its proper place. God here commands the punishment to be inflicted if anyone should have polluted himself with it.

Surely it was a detestable sacrilege to enslave to idols that offspring which was begotten for God, and which He had adopted in the loins of Abraham. In this way, they not only deprived God of His right but, as much as they could, blotted out the grace of adoption.

What He had then generally declared, He now specially applies: namely, that those who offered their offspring to Molech should be stoned. For otherwise, they would have tried to escape on the pretense that they had no intention of defecting to other gods.

Just as nowadays, under the Papacy, whatever is cited from Scripture against their impious and corrupt worship is coldly and contemptuously received, because they gloss over their idolatries and so securely indulge in them.

But after God has commanded His judges to punish this crime severely, He at the same time declares that if they should perhaps turn a blind eye to it and encourage it by their leniency, He Himself will avenge it. He will punish much more heavily those who may have escaped from human hands. Furthermore, He would implicate all those who might have been aware of it in the same condemnation.