2 Kings 18:4 He removed the high places, and brake the images, and cut down the groves, and brake in pieces the brasen serpent that Moses had made: for unto those days the children of Israel did burn incense to it: and he called it Nehushtan.
(NOTE: The children of Israel did burn incense (IDOLATRY) to it)
Numbers 21:
5 And the people spake against God, and against Moses, Wherefore have ye brought us up out of Egypt to die in the wilderness? for there is no bread, neither is there any water; and our soul loatheth this light bread.
(NOTE The people spake against God & Moses)
6 And the LORD sent fiery serpents among the people, and they bit the people; and much people of Israel died.
(NOTE: The Lord ansers with fiery serpents)
I'll speculate the fiery serpents the Lord sent to punish the peoples rebellion were: Seraphim angels
Isaiah 6:
1 In the year that king Uzziah died I saw also the Lord sitting upon a throne, high and lifted up, and his train filled the temple.
(Isaiah see's the Lord sitting high on a throne. The train = the Shekinah Glory of the Lord, who clothes Himself with light as with a garment. see Ex 33:22-23).
2 Above it stood the seraphims: each one had six wings; with twain he covered his face, and with twain he covered his feet, and with twain he did fly.
(Isaiah see's Seraphim angels: primary meaning is the burning ones. Each Seraphims had 6 wings. 2 wings covered their face, 2 thier feet & 2 to fly. The Shekinah Glory of the Lord is so great. Even fiery anglelic beings must cover thenselves in God's presents. When God's command's his mighty angels & they hearkening unto the voice of his word - psalms 103:19-21)