How do we know that Jesus Christ fulfills the requirements of righteousness?

The psalm details characteristics of a person worthy to dwell in God's presence, which are perfectly embodied by Jesus Christ. He walked uprightly, worked righteousness, and spoke the truth in His heart, thereby demonstrating the requirements laid out in Psalm 15. Unlike humanity, tainted by sin, Christ is the embodiment of moral perfection and integrity, making Him the only acceptable mediator between God and man. His actions and authority provide believers with the assurance that through His righteousness, they too can stand accepted before God.