How do we know the doctrine of the Holy Spirit's indwelling is true?

Scripture explicitly states that the presence of the Holy Spirit in a person is what defines a true believer. Romans 8:9 declares, 'If anyone does not have the Spirit of Christ, he does not belong to Christ.' It's through the Holy Spirit that one is enabled to recognize their sinfulness and their need for salvation in Christ. The distinction between the wise and foolish virgins in the parable highlights that only those who are genuinely indwelt by the Spirit will be recognized by Christ at His return.