Complex sentence: The Priestly source of the Torah says that Moses used a'fiery serpent' to cure the Israelites from snakebites (Book of Numbers, chapter 21:4-9), though the tradition of naming it Nehushtan is no older than the time of Hezekiah.
Split into simpler sentences: The priestly source of the Torah says that Moses used a'fiery serpent' to cure the Israelites from snakebites. The tradition of naming it Nehushtan is no older than the time of Hezekiah.