Verse 1: And Moses answered and said, But, behold, they will not believe me, nor hearken unto my voice: for they will say, The LORD hath not appeared unto thee.
[They will not believe, etc., וְהֵן] And behold: the ו/and is superfluous (Vatablus). Or, behold is in the place of if (Ainsworth out of the Septuagint), just like Jeremiah 3:1 (Ainsworth). They will not believe. He appears to contradict God, who had said, Exodus 3:18, and they shall harken. Response: 1. He does not simply mean that they are not going to believe; but not immediately, not by bare words, not without signs. It was sufficient for the truth of the Divine word, if they would in the end give over. 2. Moses here appears to set forth a doubt, not plainly to assert; that is to say, Behold, let us suppose that they are not going to believe me (Rivet).
They will not believe me; which he conjectured both from reason, because the greatness and strangeness of the deliverance made it seem incredible; and their minds were so oppressed with cares and labours, that it was not likely they could raise them up to any such expectation; and from the experience which he had of them forty years before, when their deliverance by his means and interest at court seemed much more credible than now it did.
Verse 2: And the LORD said unto him, What is that in thine hand? And he said, (Ex. 4:17, 20) A rod.
[What, etc.? מַזֶּה] It is the same here as מַה־זֶּ֣ה, What is this? (Munster). These three signs primarily certify the mission of Moses (Tirinus); however, mystically they designate the threefold state of the Israelites. The rod signifies their flourishing state, and the dominion of Joseph; the rod cast down and changed into a snake, the casting down and affliction of the same; the restoration of the rod, their revived liberty and power (Tirinus, Menochius, Lyra). Likewise, the leprous hand and bloody water figure this, that the Egyptians were exhausting the good health and strength, and so the vital sap and blood, of the Israelites (Tirinus). Or rather, they taught that so many and such great miracles were not accomplished by the power and hand of Moses (which was impure and leprous), but by a higher (Lightfoot’s Gleanings from Exodus 1). [These things Lightfoot further observes concerning these miracles.] It was an indication that Moses had by no means done these things by the power of the devil, because the serpent (the most prominent type of him) he was able to handle as he pleased. 2. He was commanded to apprehend its tail only, verse 4, for to meddle with the serpent’s head belonged to Christ. 3. Indeed, here it was a נָחָשׁ/serpent; in Exodus 7:10 it became a תַּנִּין, that is, a crocodile, as it appears. 4. These two miracles in a special way had respect unto that great Prophet by whose power already at that time Moses worked. For not any of the Prophets from Moses to Christ either cast out the devil, or healed leprosy by his own hand (Lightfoot’s Gleanings from Exodus).
Verse 3: And he said, Cast it on the ground. And he cast it on the ground, and it became a serpent; and Moses fled from before it.
It became a serpent, that is, was really changed into a serpent; whereby it was intimated what and how pernicious his rod should be to the Egyptians.
Verse 4: And the LORD said unto Moses, Put forth thine hand, and take it by the tail. And he put forth his hand, and caught it, and it became a rod in his hand…
[Seize the tail] There was a danger there of a strike: nevertheless, believing, Moses is not hurt (Ainsworth).