Jesus is the mediator of the new covenant. A mediator is a go-between for two parties. Just like Moses. GOD made the old covenant with Israel, not Moses, who was the mediator.
Mediator
G3316 μεσίτης mesites (mes-ee'-tace) n.
1.
a go-between
Wherefore then [serveth] the law? It was added because of transgressions, till the seed should come to whom the promise was made; [and it was] ordained by angels in the hand of a mediator [Moses]. Galatians 3:19
For [there is] one God, and one mediator between God and men, the man Christ Jesus; 1 Timothy 2:5