We have what is, honestly, one of the weirder passages from scripture today, side by side with one of the most beloved. And the reason they are side by side, is, they are connected. Jesus makes the connection, in his conversation with the Pharisee Nicodemus.
Nicodemus was a good man, though he was uncertain about Jesus, which is why he chose to visit in the middle of the night. Their conversation was wide-ranging, but at a certain point, Jesus made a startling statement. He said, “Just as Moses lifted up the serpent in the wilderness, so must the Son of Man be lifted up, that whoever believes in him may have eternal life.”
Jesus is talking about about being lifted up on the cross, and as he does, be brings in this story from the wilderness wanderings of his people. A story, frankly, in which God has kind of had it with them.
Fantoni, Giovanni. Brazen Serpent, from Art in the Christian Tradition, a project of the Vanderbilt Divinity Library, Nashville, TN. http://diglib.library.vanderbilt.edu/act-imagelink.pl?RC=55664 [retrieved January 30, 2021]. Original source: http://commons.wikimedia.org/wiki/File:Brazen_Serpent_Sculpture.jpg.