The reason Jesus is essential to believe in is because there is a holy God who is infinitely just and infinitely loving. And in his justice he is angry at us because we have sinned against him. We have rejected him, we haven’t trusted him, we haven’t loved him as we ought, we have broken his commandments. All we have to do is list out, “Thou shall not steal, thou shall not lie, thou shall not lust or covet and shall love him only above all things,” and we’ve broken those and so wrath rests upon us. Jesus is the son of God sent into the world as the atonement, the sacrifice that bears our sins and that provides our righteousness. So that if there were no Christ we would only have guilt and judgment and condemnation and Hell from God.
But because Christ came and God sent him, in his love we can look away from ourselves. This is what faith means: we look away from ourselves, we cast ourselves on Christ for his mercy and we trust his death to be our punishment.
And we trust his righteousness to be imputed to us so that now in Christ, that is in relation to Christ, by faith, God looks upon us as having fulfilled his whole law, as having all of our sins forgiven, and being acceptable in the beloved Jesus Christ. So that now we have eternal joy, eternal glory.
So the practical answer, “Why believe in Jesus” is because it’s the only way to escape Hell, to know God, to have everlasting joy in the presence of God. And we believe it because it’s true.
—John Piper
Via: Desiring God Blog