John Calvin Commentary Exodus 8:10

"And he said, Against to-morrow. And he said, Be it according to thy word; that thou mayest know that there is none like unto Jehovah our God." — Exodus 8:10 (ASV)

And he said, Tomorrow. If you refer this to Moses, there is ambiguity in the meaning; but, since it is probable that these were Pharaoh’s words, I think that he is asking for a respite until tomorrow before he lets the people go.

For those who think that he asked Moses to drive away the frogs by his prayers on the next day fall into an absurdity, as if Pharaoh went quietly to sleep and postponed the remedy for the evil.

There is, then, no basis for understanding it to mean that Pharaoh, as if his mind were quite tranquil and unmoved, desired to have his land delivered from the frogs on the following day. Rather, it means that if he were released from this difficulty, he promised the release of the people, but yet suspended it until the next day, for the purpose of deceit.

For there was no other reason for this delay, except that, having obtained what he wanted, he might go back on his commitment, as he actually did. But Moses, satisfied with this promise, undertook to bring it about that God would disperse the frogs; and this, I doubt not, was performed on the same day.

For this was the reason the tyrant changed his mind: because, with the passing of the night, his fear departed. And certainly, it is gathered from the following words that the frogs were soon after removed, for it is said that Moses and Aaron prayed after they had gone out; which would be but little in accordance with the idea that the next day was waited for.

It is not by any rash or presumptuous impulse that Moses affirmed that Pharaoh would obtain his desire, because it appears from his success that he was assured of its being God’s will. Thus, prophets, though no spoken revelation may intervene, are nevertheless often directed by the secret inspiration of the Spirit.

In this confidence, also, Moses declared that Pharaoh should know that there is no other God to be compared with the God of Israel. This, moreover, is the true knowledge of God: when whatever lifts itself up to obscure His glory is reduced to its proper level, and every high thing yields or is cast down, so that He alone may be exalted.