John Calvin Commentary Exodus 9:20

"He that feared the word of Jehovah among the servants of Pharaoh made his servants and his cattle flee into the houses." — Exodus 9:20 (ASV)

He that feared the word of the Lord. In these words, Moses shows that some were taught by experience enough not to completely despise what he had proclaimed; for from this arose their fear of the announced punishment, because they were persuaded that Moses was the servant of God, a prophet, and the herald of divine judgment.

However, it also appears that they had not seriously repented so as to obey God, but were driven to take these precautions by immediate and momentary terror.

Thus, specific fear often makes the reprobate anxious to either avert or flee from the vengeance of God.

Still, Moses says that their fear benefited them, for they did not experience the same calamity as others who were more unresponsive.

In this way, God testified that the more obstinately someone despises His judgments, the more severely and heavily they are afflicted. However, some unbelievers are spared from inconveniences to some degree and more gently chastised, because they at least do not proudly exalt themselves to despise His power.

Moreover, by this destruction, the judgment of God became more evident, as among the Egyptians themselves, whoever was most hardened received the sure reward of his contempt.

Yet we are taught by this example that it does not greatly benefit unbelievers, even if God may spare them for a time when they are alarmed and humbled, because they always remain under condemnation to eternal death.