Jesus is the Mediator of the covenant of grace. Jesus is the middleman who stands between us and God.
“Jesus is the Surety of the covenant. On our behalf, He undertook to pay our debts. On His Father’s behalf, He also undertook to see that all of the souls of His elect would be secure and safe, and that every one of the Father’s children would ultimately be presented unblemished and complete before Him.” p. 56
Jesus is the Substance of the covenant. Christ is all, and in all (Colossians 3:11).
Jesus is the Bequest of the covenant. Christ is ours and has been given to us by God.
He who did not spare His own Son, but delivered Him up for us all, how will He not also with Him freely give us all things.