How do we know Christ's death was a substitution for our sins?

The doctrine of substitutionary atonement is central to understanding Christ’s death. Second Corinthians 5:21 states that God made Christ, who knew no sin, to be sin for us, so that we might become the righteousness of God in Him. This means that on the cross, Jesus was not guilty of His own sins but bore the weight of the sins of His people. The imputation of our sins to Christ and His righteousness to us is a glorious exchange that highlights God’s justice and mercy in the act of redemption.