What does it mean for Christ to come into the heart?

The coming of Christ into the heart represents the believer's acceptance of His Lordship and the work of the Holy Spirit leading to regeneration (Hebrews 8:10). This transformation is akin to the Ark of the Covenant entering into a previously idolatrous heart, dismantling false beliefs and establishing Christ as the central figure of one’s affections and trusts. This new indwelling allows believers to experience spiritual renewal, where old idols fall and the truth of God's word prevails, setting them on a path of sanctification.