How do we know that Christ is the mediator of a better covenant?

In Hebrews 8:6, it is clearly articulated that Jesus Christ has obtained a more excellent ministry compared to the Old Covenant, thus serving as the mediator of a better covenant. This new covenant is characterized by grace rather than works, underscoring the total sufficiency of Christ's atoning work. Unlike the old covenant that demanded adherence to the law, the new covenant invites sinners to rest in the finished work of Christ. This mediatorial role of Christ assures believers that their relationship with God is not based on their performance but solely on Christ’s righteousness and sacrifice on their behalf.