John Calvin Commentary Exodus 5:4

"And the king of Egypt said unto them, Wherefore do ye, Moses and Aaron, loose the people from their works? get you unto your burdens." — Exodus 5:4 (ASV)

And the king of Egypt said to them. It is surprising that the king, in the excess of his arrogance, did not treat these servants of God more cruelly, whom he considered the ringleaders of sedition. But he was undoubtedly restrained by God from immediately proceeding to destroy them.

By his stubbornness in resisting their departure, he will more clearly show later on how important he considered it to his interests that the people should remain in Egypt. How is it then that he is content with verbal reproof and refrains from shedding their blood, if God had not protected His servants under the shield of His defense?

He harshly reproves them, indeed, and condemns them to the same labors by which the rest of the people were oppressed. But since it is well-known that moderate severity never satisfies tyrants, we conclude that they were preserved under the guardianship of God and would otherwise have died a hundred times over. But let us learn from his accusation against them as the promoters of rebellion to bear slanders and false accusations patiently, after their example; only, in reliance on God’s command, let us be fully conscious that we are unjustly accused.

The next verse, in which he says that the people of the land are now many, is intended to aggravate their guilt. This is for two reasons: first, because they would inflict a deeper injury on the public than if they had withheld only a few from their work; and second, because by inciting a large number of people, they would bring greater danger on the country.