So that we would not be condemned, Christ was condemned. God took upon himself the condemnation that we deserved. And so we read in today's Gospel: "For God did not send his Son into the world to judge the world, but that the world through him might be saved.". This year, the great feast of the Exaltation of the Holy Cross falls on a Sunday and thus gives the whole Church another opportunity to meditate on the Cross and how it is the perfect combination of divine justice and mercy. Justice demands punishment for sin. This justice must be satisfied, it cannot be ignored. But, in his mercy, God took the punishment upon himself, leaving only a small part for us to share.
The first reading shows the Israelites literally receiving the bite of the serpents as punishment for their sin. Although this actually happened, it also symbolically expresses the "bite" of sin. Every time we sin, sin comes back to bite us. We wound others with sin, but we ourselves are wounded even more, although sometimes the wound may be - and this may be the worst of all - the insensitivity of conscience to appreciate the evil we have done.
However, to save the Israelites, God tells Moses to raise up a bronze serpent, a representation of the very creature that causes their death. The Israelites are forced to face their sin, to look at it and acknowledge it. It is not surprising, therefore, that when Jesus dies on the cross, St. John quotes the prophecy of Zechariah: "They shall look upon him whom they have pierced." (Jn 19:37; Zech 12:10). We must be willing to face and acknowledge our sins so that they may be forgiven. Hence the value of confession.
Sin is shown in this episode, as with Adam and Eve, as a lack of trust in God. God then punishes, but even His punishment, in itself, is merciful: it is less than we deserve and is only meant to bring us back to Him. As we read in Ps: "And when he caused them to die, they sought him, and rose up early to turn to God.". To compensate for the disobedience of Adam and Eve before a tree inspired by pride, which led to death (cf. Gen 3:1-7 and 17-19), Christ was humbly obedient to death on a tree. As St. Paul tells us in the second reading: "he humbled himself and became obedient unto death, even death on a cross.". If we have the humility to admit our sins, the greater humility of God hastens to save us.
