Paul regarded the change from not believing in Jesus to having faith in Jesus as God's means for salvation as an event that made a fundamental difference in ethical and moral make-up of the changed person. It happened at the very root of a person. Paul described the change as:
Read more of this article about Paul and the New Creation.
We know that our old self was crucified with him so that the body of sin might be destroyed, and we might no longer be enslaved to sin.
(Romans 6:6)
In the same way, my friends, you have died to the law through the body of Christ, so that you may belong to another, to him who has been raised from the dead in order that we may bear fruit for God. While we were living in the flesh, our sinful passions, aroused by the law, were at work in our members to bear fruit for death. But now we are discharged from the law, dead to that which held us captive, so that we are slaves not under the old written code but in the new life of the Spirit. (Romans 7:2-6)
All biblical quotations, unless otherwise noted, are from the New Revised Standard Version (NRSV) of the Bible, copyright © 1989 by the Division of Christian Education of the National Council of Churches of Christ in the United States of America. Used by permission.