How do we know the Holy Spirit dwells in believers?

The indwelling of the Holy Spirit in believers is a fundamental truth of the Christian faith. Romans 8:9 states that if any person does not have the Spirit of Christ, they do not belong to Him. This assurance is a gift given immediately upon faith in Christ, as noted in Ephesians 1:13-14, where believers are sealed with the Holy Spirit after they hear and believe the gospel. The presence of the Holy Spirit signifies ownership by God and acts as a guarantee of our future inheritance. This indwelling is essential for every believer's identity and experience of salvation.