Then why was did Jesus draw a parallel between him and the snake that raised on the pole, and why raise a serpent on a pole for healing.
This is a great question. When you become a doctor, you recite the Hippocratic Oath. You don't do that in its ancient form, but the ancient form starts by invoking several gods that are more ancient than the Oath itself:
"I swear by
Apollo Physician, by
Asclepius, by
Hygieia, by
Panacea, and by all the gods and goddesses, making them my witnesses, that I will carry out, according to my ability and judgment, this oath and this indenture."
Asclepius is a hero and god of
medicine in ancient
Greek religion and
mythology. He is the son of
Apollo. In the Oath, doctors swear by Asclepius and his father and his 2 daughters.
In
Greek mythology, the
Rod of Asclepius is a serpent-entwined rod wielded by the Greek god
Asclepius. The symbol has continued to be used in modern times, where it is associated with medicine and health care.
In many cultures, snakes and serpents have been symbols of healing since ancient times and
Snake cults had been well established in
Canaan in the
Bronze Age: archaeologists have uncovered serpent
cult objects in Bronze Age strata at several pre-Israelite cities in Canaan: two at
Megiddo, one at
Gezer, one in the
Kodesh Hakodashim (
Holy of Holies) of the Area H temple at
Hazor, and two at
Shechem.
As for the Israelites who journeyed in the wilderness, we read:
Num 21:9 Moses made a bronze serpent and put it on a pole, and if a serpent had bitten any man, when he looked at the bronze serpent he lived.
Fast forward to 2
Kings 18:4, King
Hezekiah institutes an
iconoclastic reform that requires the destruction of "the brazen serpent that Moses had made; for unto those days the children of Israel did burn incense to it; and it was called Nehushtan". The term is a proper noun coming from either the word for "snake" or "brass", and thus means "The (Great) Serpent" or "The (Great) Brass".
In the
Gospel of John,
Jesus discusses his destiny with a Jewish teacher named
Nicodemus and makes a comparison between the raising up of the
Son of Man and the act of the serpent being raised by Moses for the healing of the people. Jesus applied it as a
foreshadowing of his own act of salvation through being lifted up on the cross, stating "And as Moses lifted up the serpent in the wilderness, even so must the Son of man be lifted up: That whosoever believeth in him should not perish, but have eternal life. For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life" (John 3:14–16).
Nehushtan - Wikipedia
The point is: Jesus is our great Healer.