How do we know Christ's blood is necessary for salvation?

In Hebrews, it is underscored that the Old Testament sacrificial system, which included the blood of animals, could not ultimately take away sin (Hebrews 10:4). This shows that the holiness and justice of God necessitated a perfect sacrifice, and that is found in Christ alone. His blood, as the Lamb of God (1 Peter 1:18-19), serves as the ultimate atonement that satisfies God's justice and provides remission of sins for His people. The emphasis on 'not without blood' articulates that Christ's sacrifice is central to the gospel, confirming the importance of His blood in effecting reconciliation with God.