How do we know Jesus' death is sufficient for our salvation?

The sufficiency of Christ's sacrifice lies in His identity as both fully God and fully man. As the Lamb of God, He bore the sins of His people, which enabled Him to satisfy the justice of God. This is affirmed in scripture, where it states that He suffered and died not for His own sins but for those of His people, enabling their reconciliation with God. God's acceptance of Christ's sacrifice is demonstrated by the resurrection, which shows that the price for sin was indeed paid in full. The efficacy of His sacrifice offers total assurance to believers that their sins are forgiven based upon God's justice being satisfied by Christ.