But if justification is a declaration of a God who never changes, it is as secure as God is faithful. Salvation was accomplished in the past, is experienced in the present, and guaranteed in the future. Because it was not earned, it cannot be unearned. Because it was not deserved, it cannot be undeserved. Our justification [salvation in Christ] is a past event, anchored in eternity, accomplished at the cross, declared in time, presently possessed, and which cannot be lost.
Quote from Terry L. Johnson, The Case for Traditional Protestantism: The Solas of the Reformation