Exodus 4:3

(3) A serpent.—The word here used (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 is, like nakhash, 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.)