I understand it to mean Christ Himself is the fulfillment of the law. By living the absolutely perfect life in complete accordance with every aspect of the law, He fulfilled it to perfection. So, the Law was fulfilled, or is fulfilled, in Christ. Every type or shadow in the Old Testament was perfectly brought to ultimate fruition in Him. The "until heavens and earth pass away" bit is to emphasize the eternal infallbility of the Law...

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Mason
Member, Redeemer Presbyterian Church (PCA)
New York, NY

"Come now, and let us reason together," says the Lord, "Though your sins are like scarlet, they shall be as white as snow; though they are red like crimson, they shall be as wool." - Isaiah 1:18