What does the Bible say about the heart in relation to true religion?

Scripture clearly states that the heart is the seat of true religion. In Romans 2:28-29, Paul explains that true circumcision is of the heart, achieved by the Spirit, indicating that outward appearances alone are insufficient for genuine faith. A man may demonstrate the forms of religion externally—attending services or participating in rituals—but if his heart is not transformed, he lacks true Christianity. God commands our hearts, desiring sincerity and authenticity in our relationship with Him, which highlights the importance of heart-based faith over formal practices.