Therefore the people came to Moses, and said,
We have sinned, for we have spoken against the Lord,
and against thee; pray unto the Lord that he take away the serpents from us.
Numbers 21:7
"For this nation of shepherds, the serpent lifted on a pole served as a strong symbol which they all well understood. Snakes are a deadly menace to sheep. A dog might get bit by a rattlesnake and survive without any special treatment, but sheep are much more fragile. This is one of the reasons why shepherds must carry a rod."Doug Batchelor