Exodus 4:3-4

It became a serpent Was really changed into a serpent. There was a significancy in this sign: it intimated what and how pernicious his rod would be to the Egyptians. It became a rod in his hand When stretched forth by the hand of Moses or Aaron, it became a token to Israel of guidance, encouragement, and protection; but to Egypt, like the bite of the most poisonous serpent, it betokened desolating judgments.