Therefore, since we have been justified by faith, we have peace with God through our Lord Jesus Christ.
Romans 5:1

Peace is a state of relationship between us and God. This isn’t talking about a clear conscience, but about escaping God’s wrath. Those who are not justified in God’s eyes will receive his wrath at the final judgment if not before.

See Isaiah 27. Repentance brings peace with God, which brings restoration and fruitfulness.