Christians believe in both the old and new testaments. They complete the word of God. They fit like a puzzle. The new testament is a fulfillement of the old. So it's not that we don't believe in the old testament, it's that we feel it doesn't apply to modern day. If you go by the old testament law, we would all be guilty of death. In the law it states that even if you keep the entire law and offend it in one point, you would be guilty of the whole law. One sin equals death. Even if you were a very holy person but had an evil thought, you're a gonner. The law convicted everyone of sin. We no longer live under this very strict law. Jesus nailed the law to the cross. We now live by Grace. The gift of God is ETERNAL LIFE.