How do we know Jesus is our Mediator of a better covenant?

In Hebrews 8:6, it speaks of Jesus as the Mediator of a better covenant than that of the old covenant of works. The new covenant promises eternal blessings and is based on the power of Christ’s endless life. Unlike the old covenant mediated by mortal men who had to offer sacrifices repeatedly, Jesus’ mediation results in an eternal promise of salvation, reconciliation, and justification for all who come to God through Him. This underscores the supremacy of grace over the requirement of law.