John Calvin Commentary Exodus 4:2

"And Jehovah said unto him, What is that in thy hand? And he said, A rod." — Exodus 4:2 (ASV)

What is that in thine hand? In accordance with the idiom of the Hebrew language, Moses now explains more fully, and more distinctly pursues, what he had before only generally alluded to regarding the signs. In the three signs to which he refers, we must consider their respective meanings. The pastoral crook, which he carried in his hand, is thrown on the ground and becomes a serpent; again, it is taken back into his hand and recovers its original nature.

I do not doubt that God wished to show him that, although his condition was abject and despicable, he would still be formidable to the king of Egypt. For his rod was the symbol of a shepherd; and what would be more contemptible than for a keeper of sheep to come up from the desert and oppose the scepter of a most powerful king with that crook, by which he could scarcely protect himself and his flock from wild beasts? But God assures him that, although deprived of earthly splendor, wealth, or power, he would still be terrible to Pharaoh. This was as much as to say that he did not need to fear that Pharaoh would despise him or take no account of him as a mere rustic, because his rod, turned into a serpent, would inspire more terror than a thousand swords.

Regarding what Moses says, that he himself fled from it in alarm, unquestionably God intended to frighten His servant, so that he might better estimate from his own feelings what the power of God would be to terrify that proud king. This, then, was the object of the miracle: there was no need for mighty armies, since Pharaoh would tremble at the sight of the simple rod. Furthermore, the rod did not need to be wielded and violently agitated, because it would inspire sufficient terror by its own movement and agitation. The part of the miracle where the rod returned to its former shape was intended to show Moses that what was to be hostile and injurious to his enemy would be an assistance and safeguard to himself. Therefore, the same rod that encouraged and emboldened Moses, depressed and overwhelmed his foe.

But that he dared, in immediate obedience to the voice of God, to lay hold of the serpent is a proof of his remarkable faith. This appears more clearly from his sudden change: he did not fear to provoke a poisonous and noxious animal by taking hold of its tail, when he had so recently fled from its very sight in consternation. His timid mind, then, was capable of great courage, and his timidity and piety brought forth their fruit alternately. And this is especially worthy of remark: Moses was strengthened by the presence of God, but he was weakened when he turned his eyes to the untamable minds of his own people and to the proud tyranny of Egypt.

The question now arises: was the change of the rod into a serpent real and actual, or was only the outward form changed? Although I would be unwilling to contend tenaciously for a matter of little consequence, I embrace the more probable opinion: not merely an image or vision appeared, but God, who created all things out of nothing, gave a new nature to the rod and again made a rod out of the serpent. This was in no way more difficult than to change Lot’s wife into a pillar of salt (Genesis 19:26). Since this was easy for God’s power, it does not seem likely to me that He resorted to the illusion of visions.

As for the imitation by the magicians, we will speak of their sorceries in their proper place.