Because God is perfect and just our sin cannot go unpunished. The punishment for sin is death. Each person can never hope to save themselves from the consequences of sin in life by their own means; neither by some sort of commendable human effort (good deeds) or by some sort of religious practice (ritual). God’s plan is to enable humans to rely on trusting in Him to rescue them. We can only be saved from the future consequences of our sin by repenting, trusting Jesus and having faith in what His death and resurrection achieved. Through this process God’s Spirit births and begins to grow in us a new future resurrection life that Jesus has made possible. However, for now, the Christian lives in a state of tension. On one hand by God’s Spirit, we have this new capacity to live a life that should increasingly give a real glimpse of the new humanity of the future. On the other hand, we still possess an old nature with its very real potential to sin. For every Christian this rebirth (or being ‘born again’) will eventually come to completion, and the tension finally resolved, on our resurrection from death when Christ returns. In the mean time the Christian is commanded to no longer live by the old nature but to daily seek through God’s Spirit to live by the new nature.