The Bible is the foundation of Christian thought. Many have strayed from orthodoxy over the centuries, and many have never heard the gospel. The solution for both is the same: studying the Bible to see that it’s true. Of special concern should be the life and teachings of Jesus and His first followers.
We who follow Jesus take part in the new covenant, but some are confused about whether Christians are included in the old. Here we see in Matthew 17 that Jesus' followers are exempt from the Law because we are children of the King.