A friend asked me to comment on the theory that Aaron’s staff may have become a crocodile, rather than a snake, in Exodus 7:8-12. The Hebrew word used throughout is tannin, which can mean a dragon, a serpent, a sea monster—really any large, serpentine reptile.
The theory is based on crocodiles being closely associated with the god Sobek. In many historical sources, pharaohs were seen as having affinity with Sobek, and some even took him as their personal deity. Could the staff miracle in Exodus 7 be a case of God demonstrating his power over Pharaoh by showing who was really in charge of crocodiles—essentially shaming him by usurping the domain and power of Sobek?
I don’t think so. It’s not a bad theory overall. But while it’s true that crocodiles were associated with Sobek, and Sobek was sometimes associated with the power of the pharaoh (what god wasn’t?), there are several lines of evidence that strongly favor tannin in Exodus 7 referring to a snake—probably an Egyptian cobra:
1. Intertextual evidence
Moses explicitly uses tannin in Deuteronomy 32:33 to refer to Egyptian cobras (asps). So while the semantic range of the word could include crocodiles, we have no clear example of that usage from Moses; but we do have a clear example of usage with reference to asps.
In Exodus 4:3 Yahweh gives Moses a “practice run” for this encounter with Pharaoh and his magicians. Moses throws down the staff as commanded, and it becomes a nachash—which is certainly a snake of some kind, and not a crocodile. This event is obviously intended to prefigure the encounter in Exodus 7; ie, the implication is that the very same thing happened there. But in that case, tannin should be understood as a snake, not a crocodile.
2. The polemical theology argument works better with an asp
The idea here is that, in this confrontation, God is demonstrating his power over the deities of Egypt (including Pharaoh). John Currid, who is at the forefront of Egypt-related Old Testament interpretation, calls this polemical theology. Certainly that is what is going on here.
But the polemic is much stronger if the staff turned into an asp, because the asp was the symbol of Pharaoh’s divine status and power. The asp (uraeus) he wore on his crown represented the divine commission of the goddess Wadjet, who was the protector of lower Egypt. It was what authenticated Pharaoh as a god himself, and gave him the right to rule. So Aaron’s staff turning into an asp would be a direct confrontation to Pharaoh’s power and rule; its consuming the other asps created by Pharaoh’s magicians would represent, to the Egyptians, Moses and Aaron destroying and even absorbing Pharaoh’s power.
The same cannot be said if the staff became a crocodile. While that would have some polemic value, it would be significantly weaker—less pointed, less focused on Pharaoh’s power and right to rule.
3. Socio-religious evidence
The ability to manipulate snakes in particular was a trademark of Egyptian magic. Egyptian priests were snake-charmers; a group called the Psylli were well-known for being able to stretch snakes into rigid “staffs” by putting them into a state of catalepsy—which could then be undone on command. The confrontation fits neatly into this context if tannin means snake; not so if it means crocodile.
The ability to transform inanimate objects to animate ones was also found in Egyptian magic. An example is a priest who was said to transform a wax crocodile into a real one, and then back to wax when he picked it up by the tail. So Exodus seems to be playing off this motif. But the fact that it is a staff which transforms here strongly suggests that it turned into an asp, not a crocodile—because the form of the inanimate object seems important for what it becomes. A wax crocodile becomes a real crocodile; but a staff does not look like a crocodile. It has far more resemblance to a stretched-out snake.
Some helpful resources on this: