How do we know that we have the Holy Spirit in us?

Believers are assured of the Holy Spirit's presence by their faith in Christ, which is described as the firstfruits of the Spirit. This inner confirmation often results in a deep awareness of the struggle against sin and the longing for redemption mentioned in Romans 8:23. When one truly believes in Christ, there is a transformation within, leading to a changed heart that senses the need for God’s grace. The presence of the Holy Spirit is also a promise from God, sealing believers as heirs of salvation, as affirmed in Ephesians 1:13-14.