How do we know that regeneration leads to newness of spirit?

Regeneration results in newness of spirit as stated in Romans 8:9, which emphasizes that those who have the Spirit of God dwell in the Spirit. This transformation gives rise to genuine faith and repentance, which are inseparable fruits of the Spirit's work within believers. When one is born again, they recognize their former state of sin and are enabled to turn to Christ in faith, reflecting a life that no longer seeks righteousness through the law but through Christ alone. This transformation confirms the truth of the doctrine of regeneration as a divine act that produces lasting spiritual change.