Romans 8:9 “But you are not in the flesh but in the Spirit, if indeed the Spirit of God dwells in you. Now if anyone does not have the Spirit of Christ, he is not His.” (NKJ)
Revelation 3:20 "Behold, I stand at the door and knock. If anyone hears My voice and opens the door, I will come in to him" (NKJ)
Christ cannot "come in" to anyone UNTIL that person HEARS and then OPENS their heart door.
The drawing of God's spirit IS the "knocking". The "measure of faith" enables the person to OPEN their heart to more of the spirit. But the "measure" and the "knocking" DO NOT RENDER A PERSON SAVED, and they DO NOT mean that a person has been "born again from above". The "born again" person has actually OPENED their heart to Christ.
If Jesus is on the OUTSIDE "knocking" - He has NOT YET "come in".
Before the Damascus road, Paul was NOT indwelt by the Spirit of Christ. He may have been under conviction, but he had NOT YET opened his heart door to Jesus. Paul sites two men whom he says were "in Christ BEFORE ME". This tells us that Paul did not regard himself as always having been "in Christ". There was a specific TIME when Christ came "in" to Paul, and Paul came to be "in Christ".
Romans 16:7 “Greet Andronicus and Junia, my countrymen and my fellow prisoners, who are of note among the apostles, who also were in Christ before me.”