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

Jesus' death on the cross is the cornerstone of Christian faith and is vividly portrayed in Isaiah 53, which details how He bore our griefs and carried our sorrows. Verses such as 'He was wounded for our transgressions; he was bruised for our iniquities' demonstrate the substitutionary nature of His sacrifice. These words affirm that Christ suffered not for His own sins, but for the sins of His people. The death of Christ was a voluntary act, where He willingly took upon Himself the penalty of sin to satisfy God's justice. This is crucial because it establishes that our sins were laid upon Him, and in believing in Christ, we receive the benefits of His payment for that debt. The author of Hebrews reinforces this idea when referring to Christ as our great high priest, completing the work of atonement once and for all.