What does the Bible say about mouth confession and heart belief?

Romans 10:9-10 emphasizes that confession with the mouth and belief in the heart are intrinsically connected to salvation. This means that true faith is not just a superficial acknowledgment of Christ's lordship but a deep-seated belief that God raised Him from the dead. This heart belief is said to bring about righteousness, while the outward confession is a demonstration of that inner faith. Thus, one cannot truly call upon the name of the Lord without first having been regenerated to believe in Him from the heart.