Just as Moses lifted up the snake in the wilderness, so the Son of Man must be lifted up, that everyone who believes may have eternal life in him."
For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life. For God did not send his Son into the world to condemn the world, but to save the world through him. Whoever believes in him is not condemned, but whoever does not believe stands condemned already because they have not believed in the name of God’s one and only Son. (John 3:14-18, NIV)
When the Israelites were wandering in the wilderness following their exodus from the slavery of Egypt, they grew tired of their diet and grumbled against God and against Moses, ""Why have you brought us up out of Egypt to die in the wilderness? There is no bread! There is no water! And we detest this miserable food!" (Numbers 21:5). As a punishment God sent poisonous snakes among them, biting and killing many of them. Realizing their sin, they turned to Moses and asked him to intercede for them with God. As a result, God had Moses fashion a bronze serpent and hang it on a pole. Any Israelite who was bitten need only look at this serpent, believing that God would heal him, and he would not die.
In the same way, we are saved. While we may not be bitten by poisonous snakes, we have been bitten with the fatal poison of sin. However, just as God provided a way for the Israelites bitten by the fiery serpents to be saved, He has also provided a way for us, bitten by the poisonous sin of the devil, the world and our own flesh, to be saved. If we look to the cross of Jesus, believing that God will heal us from our sin, then we will be saved. It’s that simple!
We tend to complicate the message of Christianity. We throw in multi-syllable words like justification, propitiation and sanctification to describe our theology, another large word that simply means "what we believe about God". We argue transubstantiation versus consubstantiation versus the confusing phrase "in, with and under" in describing Holy Communion. We use Latin phrases like "sola scriptura", "simul justus et peccator", and "crux theologorum" in describing what we believe, often confusing matters further. Even our use of simple words like "sin" and "faith", which have been so misused that different people have very different understandings, makes Christianity seem more difficult.
However, Christianity is not that complicated. We are born in sin, and we spend our entire lives sinning; that is, we disobey God’s commands on how we are to live our lives (i.e., we sin). Because God is just (i.e., He is completely fair), our sins, our disobedience, must be punished. The just penalty for our sins, what we truly deserve, is suffering in this lifetime and eternal damnation, suffering forever in Hell.
This is where Jesus comes into the picture. Because God loves us, even though we are miserable sinners and, by nature, enemies of God, Jesus, the second person of the Triune God, became man, lived a perfect, sinless life, only to be falsely accused and suffer a horrible, excruciating death on a cross, an utterly cruel form of torture and death. In so doing, God the Father, the first person of the Triune God, took out His wrath, the punishment for our sins, on His Son as He hung dying on the cross. As a result, since Jesus has already paid the penalty for our sins, we, like the Israelites bitten in the wilderness by the poisonous snakes, need merely look to the cross, trusting that Jesus has died for our sins, and we will be saved (i.e., we will not have to pay the penalty for our own sins). It’s that simple!
If our faith, what we believe and trust, is not in Jesus, then we will pay the penalty for our sins. We will spend eternity suffering in the fiery pit as the just punishment for our sins. Nothing we do in this lifetime, other than trusting in Jesus as our Lord and Savior, can save us from this righteous judgment. We can spend our entire lives helping others, we can give away all our possessions, and it simply won’t matter. There is one way, and only one way, to be saved, and that is by trusting in Jesus as our Lord and Savior!
In summary, we sin; that is, we disobey God. Our sins must be punished. Jesus died on the cross to take on the punishment for our sins. Therefore, we cling to the cross, trusting that Jesus has already paid the penalty for our sins. It’s that simple!