For two whole chapters (Exodus 3-4), Moses does just about everything he can to get out of going to Egypt. He asks for a name as to who is actually sending him to Pharaoh, tells God that he’s not a good speaker, and finally just begs God to send someone – anyone – else.
One of those excuses is the question of verification: What if the people don’t believe that God sent me?
To remedy this, God asks him to throw the shepherd staff that is in his hand to the ground. When Moses complies, it becomes a snake. Moses immediately begins to run, since snake bites then and now can be fatal. Moses’ response is absolutely rational.
Then, God tells Moses to pick the snake back up, but not at the head, where he could prevent the snake from biting him, but at the tail. Again, Moses complies, and the serpent turns back into a staff.
Eventually, this staff-to-serpent-to-staff sign will be the first miracle that Moses does before Pharaoh. Initially, Pharaoh is impressed, until his own magicians are able to “replicate” the sign. This type of magic is imitated by real-life snake handlers today, who are able to cause snakes to go unconscious, which makes them look exactly like a stick.
This wouldn’t be the last time Moses has an interaction with snakes. In the wilderness during a period of excessive complaining, God allows serpents to travel through the camp and bite the people, resulting in death. The only thing that saves them is a bronze serpent that Moses erects in the middle of the camp. Those who looked at it survived the bite (Numbers 21:6-10).
Snakes also played a role in Egyptian mythology. The snake is the symbol of the Pharaohs, so one possible reason for this specific type of sign is to show God’s dominance of the nation of Egypt.
I’ve often wondered why God chose this sign first, knowing that the magicians of Egypt would be able to “replicate” the sign for Pharaoh. I still don’t have a good answer, but I think it’s possible that by pitting Moses against the best magicians in the land at the outset, it set the stage for how much larger the rest of the plagues would be.
The magicians could only imitate Moses’ signs for so long; once they were unable to match him, it was obvious that a higher power stood behind Moses.