What is the indwelling of the Holy Spirit?
“…But if anyone does not have the Spirit of Christ, he does not belong to Him.”
— Romans 8:9
At the very moment of salvation the Holy Spirit baptizes believers into the Body of Christ and comes to live inside them from that moment forward.
(Taken from “Know the Truth:60 Questions and Answers on Christian Beliefs” from First Baptist Church in Tallassee, Alabama; Based on the 2000 Baptist Faith & Message)