It was in the form of a serpent that the evil spirit entered into the garden of innocence and tempted the first human beings. Thus it should be no surprise that serpents came to afflict the Israelites who had complained against God and Moses (see Numbers 21: 4-9). The serpents were a consequence of turning from God. But what is surprising is that an image of this evil, the serpent, became the source of healing. God told Moses to make an image of the serpent and to fix it on a pole. Anyone who had been bitten by the serpent would find healing by looking upon the mounted serpent.
Even more surprising, Jesus uses this image of the serpent to refer to himself. He told Nicodemus that "just as Moses lifted up the serpent in the desert, so must the Son of Man be lifted up, so that everyone who believes in him may have eternal life" (John 3: 14-15). How is it that Jesus uses this image of evil for himself?
St. Paul helps us understand this. He wrote: "Christ ransomed us from the curse of the law by becoming a curse for us, for it is written, 'Cursed be everyone who hangs on a tree'" (Galatians 3: 13). He also wrote: "For our sake God made him to be sin who did not know sin, so that we might become the righteousness of God in him" (2 Corinthians 5: 21). Christ "became sin" and in that way became the source of healing and new life. He identified himself totally with sinful humanity and took upon himself the sins of the world.
He also took upon himself the consequences of sin. Again, St. Paul: "And even when you were dead in transgressions and the uncircumcision of your flesh, he brought you to life along with him, having forgiven us all our transgressions; obliterating the bond against us, which was opposed to us, he also removed it from our midst, nailing it to the cross..." (Colossians 2: 13-14). Jesus took upon himself the judgment, the result of sin, and allowed it to be nailed into his own body on the cross. He made reparation, repairing the damaging consequences of sin, by offering himself on the cross.
In another place in John's gospel, Jesus refers to his being lifted up. He said: "When you lift up the Son of Man, then you will realize that I AM..." (8: 28). How is it that people will realize that Jesus, when he is lifted up on the cross, mounted like the serpent, a curse and sin, is God, I AM? Because God is love (1 John 4: 8, 16). What proves love? What is the greatest sign of love? What proves that Jesus is Divine Love itself?
St. Paul answers: "For Christ, while we were still helpless, yet died at the appointed time for the ungodly. Indeed, only with difficulty does one die for a just person, though perhaps for a good person one might even find courage to die. But God proves his love for us in that while we were still sinners Christ died for us" (Romans 5: 6-8).
Christ continues to give proof of his love when he is lifted up at Mass. At every Sacrifice of the Mass he makes present his life-giving death on the cross. Our faith is that Jesus is God and that he is present in the lifting up at Mass. His Body and Blood, lifted up, overcome sin and death. The serpent is defeated.