John Calvin Commentary Exodus 10:12

"And Jehovah said unto Moses, Stretch out thy hand over the land of Egypt for the locusts, that they may come up upon the land of Egypt, and eat every herb of the land, even all that the hail hath left." — Exodus 10:12 (ASV)

And the Lord said to Moses. Since Pharaoh was not persuaded to obey by the announcement of the punishment, its execution is related here. First, Moses is commanded to stretch out his hand to bring in the locusts, by virtue of the authority with which God had invested him, for stretching out the hand is a sign of power.

He therefore adds, a little later, that he stretched out his rod, which we have previously seen was given to him as a royal scepter. It is, then, just as if God had appointed him to be His vicegerent and had subjected the sea, the earth, and the air to him.

But, to properly establish his role as a minister, he does not say that the locusts came up at his command but attributes the glory of the action to the Lord alone. This manner of expression is noteworthy, since we learn from it that the ministers of God, although they bring nothing of their own, still do not labor in vain, because the efficacy of the Spirit is joined with their word. Furthermore, nothing is taken away from the power of God and transferred to them, since they are only instruments, which God’s hand uses in His service.

Thus, Moses did not command in vain, as he stretched out his rod, for the locusts to come up, because the effect of his command immediately appeared. Still, he did not himself create the locusts, nor attract them by the stirring of his rod; instead, they were divinely brought by the power of the east wind.

But such a sudden gathering unquestionably occurred contrary to the natural order; nor, if God used the wind in this way, does it necessarily mean this was a usual occurrence. We know that the east wind is a beneficial and gentle wind, and although it is sometimes stormy in relation to Judea, it still does not seem likely that Egypt was covered with locusts either by its strength or by its destructive blast.

It is possible, however, that God, by bringing in the immense number of locusts with a sudden whirlwind, gave the Egyptians a sign of their approaching calamity, so that it might be more evident that the locusts had not arisen in any other way than according to the prediction of Moses.

That before them there were no such locusts as they, neither after them shall be such, is no contradiction to the declaration of Joel, who also affirms that such an instance had never occurred, as that the locust should eat what the palmer-worm had left; and what the locust had left the canker-worm should eat; and what the canker-worm had left the caterpillar should eat (Joel 1:4). For he is not there speaking of a single punishment, but of its varied and multiform continuation.