How do we know that Christ is the fulfillment of the Old Covenant?

The Old Covenant contained types and shadows of greater truths fulfilled in Christ. Moses, the high priest, and the sacrificial system all pointed to Jesus, who would become the true mediator and perfect sacrifice. Christ's role in fulfilling the law demonstrates that the righteousness required by God is attained not through the Old Covenant's sacrifices, but through His own sacrificial death. His blood is the only thing that can truly cleanse us from sin, establishing the New Covenant where all believers are justified through His grace.