How do we know that justification is by faith in Christ?

In Galatians 2:16, Paul affirms that 'a man is not justified by the works of the law but through faith in Jesus Christ.' This assertion underscores the Gospel's core message that salvation is a gift, obtained through faith alone and not human efforts. Justification, in sovereign grace theology, is an act of God's grace where He declares sinners righteous based solely on Christ's righteousness imputed to them. The law reveals our inability to achieve righteousness, thus highlighting our need for Christ, who fulfills the law on our behalf. Faith in Him is what unites us to this justification, ensuring that our standing before God is secure, rooted not in our merit but in Christ's perfect work.