Charles Ellicott Commentary Exodus 4:3

"And he said, Cast in on the ground. And he cast it on the ground, and it became a serpent; and Moses fled from before it." — Exodus 4:3 (ASV)

A serpent. — The word used here (nakhash) is a generic one for a snake of any kind and tells us nothing as to the species. A different word (tannin) is used in Exodus 7:10, while nakhash recurs in Exodus 7:15. Tannin, like nakhash, is a generic term.

And Moses fled from before it — It was natural for Moses to remember his alarm and record it. Any later writer would have passed over so small a circumstance. (See the Introduction, p. 3.)