Why is understanding the heart important for Christians?

The condition of one's heart is a central theme in Jesus's teaching, particularly illustrated in Matthew 15:18-20, where He emphasizes that what comes out of the mouth is reflective of the heart and that our hearts are the wellspring of moral and spiritual corruption. Recognizing the heart's true state – as 'deceitful above all things' (Jeremiah 17:9) – is vital for Christians because it underscores our need for Christ’s redemptive work. Only through Him can we receive a new heart (Ezekiel 36:26) and approach worship with sincerity and truth. Thus, understanding the heart leads to a depth of repentance and reliance on God's grace.