What does it mean that Christ fulfills all righteousness?

The phrase 'fulfilling all righteousness' encompasses Christ’s entire obedience to the law and His substitutionary work for His people. As indicated in Isaiah 42:21, the Lord is pleased for His righteousness' sake, signifying that through Christ, the law is honored and magnified. He did not merely make salvation possible; He accomplished it through His perfect obedience from birth to crucifixion. He fulfilled the law's demands and bore the wrath of God against sin on behalf of His people, ensuring that they are justified. This establishes a firm foundation for believers, highlighting that their relationship with God is based solely on Christ's fulfillment of righteousness, not their own efforts.