How do we know that Christ's righteousness protects us?

The assurance of Christ's righteousness lies in the doctrine of justification by faith, as expressed in Romans 4 and 5. When we place our faith in Jesus, we are justified, meaning that we are declared righteous before God. This declaration comes from an alien righteousness, which is not our own but that of Christ. Thus, when Satan accuses us, reminding us of our sins and shortcomings, we can confidently respond that our hope rests not in our performance but in the perfect obedience of Christ. This breastplate of righteousness serves to protect our tender consciences from despair, allowing us to stand firm in the truth of the gospel that assures us of our acceptance in the beloved (Ephesians 1:6).