When GOD sent venemous snakes upon Israel to punish them for their complaining, the snakebitten person that looked upon the bronze snake on a pole would be healed.
After defeating Arad, Israel returned to their incessant complaining against Moses and GOD. This time, GOD sent venemous snakes into the camp.
Admitting their sin, once more, Israel asked Moses to intercede with GOD. GOD provided a unique remedy:
4 Then [Israel] departed from Mount Hor by the Way of the Red Sea; and they went around the land of Edom, and the people became discouraged on the way. 5 So the people spoke against God and against Moses, “Why did you bring us up out of Egypt to kill us in the desert? For there is no bread nor water, and our soul is weary of this worthless bread.” 6 So the Lord sent venomous serpents among the people, and they bit the people; and many of the children of Israel died. 7 Then the people came to Moses, and were saying, “We sinned, for we spoke against the Lord and against you; therefore, pray to the Lord, and let Him take away the serpent from us.” So Moses prayed for the people. 8 Then the Lord said to Moses, “Make a serpent for yourself and put it on a signal pole; and it shall be, if a serpent should bite someone, when the one bitten looks at it, he shall live.” 9 So Moses made a copper serpent and put it on a signal pole; and it happened, when a serpent bit anyone, and he looked at the copper serpent, he lived.
(Numbers 21:4-9 OSB)
The serpent pole served as a shadow of a future time when Israel's Messiah would be raised up on a pole (cross) and faith in Him would save a sinner from the snakebite of The Serpent's temptations.
Later in Israel's history, we learn that King Hezekiah ultimately destroyed the bronze snake pole because Israel had been offering incense to it, idolatrously (see 2 Kings 18:4).