John Wesley emphasizes the significance of the heart in true religion, asserting that belief and justification come from the heart rather than mere understanding. He explains that confession with the mouth is essential for salvation, linking it to the concept of justification, which is God's act of declaring believers righteous through faith in Christ. Wesley highlights that justification is not just forgiveness but a declaration of righteousness that fulfills the law, allowing believers to embrace their relationship with God fully. He encourages a heartfelt belief that leads to genuine outward expressions of faith, reflecting the teachings of the Sermon on the Mount.