“The Son of Man must be lifted up... so that everyone who believes may have eternal life in him” (Io. 3, 14-15). The human family had received at the very beginning of earthly history a deadly bite from the “ancient serpent.” He had injected a satanic venom – the venom of original sin – into the souls of the first man and woman. And from that time onward, man’s history on earth has been burdened by sin. A tendency towards sin has generated many evils in the lives of individual persons and the communities to which they belong, in families, in entire peoples and nations.
“The Son of Man must be lifted up,” says Jesus to Nicodemus. And he says this with a view to his crucifixion: The Son of Man must be lifted up on the Cross. Whoever believes in him, whoever sees in this Cross and in the Crucified One the Redeemer of the world, whoever looks with faith on the redemptive death of Jesus on the Cross, finds in him the power of eternal life. By this power, sin is overcome. People receive forgiveness of their sins at the price of the Sacrifice of Christ. They find again the life of God which had been lost by sin.
-Homily of Blessed John Paul II, Feast of the Triumph of the Cross 1988