How do we know justification is true in Christian theology?

Justification is established on the principle that our right standing before God is through Christ alone. Romans 5:17 clearly states that through Christ's obedience, many are made righteous. This means that our justification does not come from our works but from Christ's. The very essence of justification asserts that believers are counted righteous before God because they are united to Christ, who fulfilled the law perfectly on our behalf. Therefore, it is not our faith or works that justify us, but solely God's grace through faith in Christ. This aligns with the Reformed understanding of salvation, emphasizing that it is a gift rather than a merit-based achievement.