In the book of Numbers, there's a weird story about Moses, God, and some snakes. The people were complaining about all the traveling, and didn't care much for the bread that God was providing everyday. So, God sends some poisonous snakes and they bit a bunch of people who died. Of course, the people took back their words and begged Moses to make God stop hurting them. To heal the people, God told Moses to make a bronze figurine of the poisonous snake and put it on a pole. If one was to be healed, he had to look into the eyes of the snake.
Jesus tells Nicodemus that the Son of Man has to be lifted up just like Moses lifted up the snake in the wilderness. Isn't that a little strange?
Jesus isn't just comparing himself to this thing that heals and gives life. He's also comparing himself to this thing that harms and gives death.
Remember when Jesus said something like you gotta lose your life to gain it? I think it has something to do with that. According to the text, God sent the snakes and he also sent Jesus. When the snakes bit the people, it prompted them to repent. When Jesus talks to people, he calls them to repentance. When the people looked into the eyes of the snake sent to change them, they were healed. And when people look into the eyes of Christ, I guess the same thing happens.
But what do I know?