How do we know Christ's sacrifice is effective for believers?

The effectiveness of Christ's sacrifice is rooted in the fulfillment of God's law. As outlined in Romans 5:19, through the obedience of one (Christ), many are made righteous. His shed blood is the basis upon which God can justly forgive sinners, as it answers the law's demands for punishment. The blood of Jesus Christ cleanses from all sin (1 John 1:7) and secures the new covenant, where believers are assured of salvation. This assurance is grounded in faith, as believers receive Christ as He is presented in Scripture, acknowledging both His sacrifice and their need for grace.