The main source for the Christian tradition of redemption is the New Testament, which is filled with verses about redemption. In the Christian tradition, God is angry and alienated from humans because we sin: we are cruel when we should be kind, hateful when we should be loving, judgmental when we should forgive. Our behavior leaves us in a living hell of sorts, apart from God's love and grace. However, if we follow Jesus and his radical way of love, peace, and forgiveness, we can be redeemed or made worthy in the eyes of God.
The most famous verse expresses this idea of redemption through Christ:
For God so loved the world, that he gave his only Son, that whoever believes in him should not perish but have eternal life.
Although this verse is often misunderstood as meaning that saying a few words as an incantation gives us a magic force field that compels God to let us into heaven, the meaning of the word "believes" implies action. If we believe in the way Jesus lived and preached enough to practice his lifestyle and follow his advice, such as loving those who hate us or not accumulating wealth, we begin to become cleansed or redeemed in front of God.
Another source for the Christian tradition of redemption is the Old Testament, now often called the Hebrew Bible. The Hebrew Bible introduces the concept of covenant with God. This is a transactional relationship in which the Israelites receive God's special protection as long as they follow his commands. They are redeemed through obeying his law. This becomes the foundation for the shift in Christianity
in which Christ redeems sinners.
Isaiah is a foundational text from the Hebrew Bible that Christians read as foretelling the coming of Christ. Christians interpret such verses as the following as foreshadowing
Christ's redemptive role, seeing the "I" in the statement as meaning Jesus:
I have blotted out your transgressions like a cloud and your sins like mist; return to me, for I have redeemed you.
In short, believing enough in Christ's message to try to live it, even if this will inevitably be imperfect, begins to redeem humans. To the extent that we will always fall short of perfection, according to Christian theology, we cannot achieve redemption on our own. Here, Jesus fills in for us and takes the punishment that is due to us, illustrated by his undeserved death on the cross.