How do we know the concept of substitutionary atonement is true?

The doctrine of substitutionary atonement asserts that Christ died for His people, serving as their representative before God. In Romans 6, Paul discusses how Christ's death achieved this substitution for believers, affirming that those united to Him in His death are thus freed from sin. This understanding aligns with the historic Reformed view that Christ's sacrifice fully satisfied the demands of justice on behalf of those He came to save. The truth of this doctrine is evidenced in Scripture and experienced in the transformation of believers' lives who are enabled to walk in newness of life, free from the bondage of sin.