How do we know God's promises in the Old Testament are fulfilled in Christ?

The New Testament confirms the fulfillment of Old Testament promises through the person and work of Jesus Christ. For instance, Hebrews repeatedly emphasizes how Jesus is the ultimate fulfillment of the sacrificial system established in the Old Testament. His sacrifice, likened to the blood of the everlasting covenant, guarantees the completion of God’s promises. As stated in Romans 10:4, Christ is the end of the law for righteousness to everyone who believes, signifying that the entirety of God’s redemptive plan culminates in Him.