How do we know that Jesus' sacrifice was necessary for our salvation?

In Hebrews 10:4-10, it is clearly articulated that the blood of bulls and goats cannot take away sins, highlighting the inadequacy of the Old Testament sacrificial system. Instead, this passage reveals God's purpose in sending His Son, Jesus Christ, who declared, 'Lo, I come to do Thy will, O God.' This establishes the New Covenant, through which believers are sanctified by the body of Jesus Christ offered once for all. The necessity of Christ's sacrifice is further affirmed by its unique sufficiency, indicating that through Him, we gain access to God's mercy and grace, which fulfills the requirements of the law while offering true forgiveness.