'Go between' in the Bible

This is the one who was in the congregation in the wilderness together with the Angel who spoke to him on Mount Sinai, and who was with our fathers; and he received living oracles [divine words that still live] to be handed down to you.

Why, then, the Law [what was its purpose]? It was added [after the promise to Abraham, to reveal to people their guilt] because of transgressions [that is, to make people conscious of the sinfulness of sin], and [the Law] was ordained through angels and delivered to Israel by the hand of a mediator [Moses, the mediator between God and Israel, to be in effect] until the Seed would come to whom the promise had been made.

Now the mediator or go-between [in a transaction] is not [needed] for just one party; whereas God is only one [and was the only One giving the promise to Abraham, but the Law was a contract between two, God and Israel; its validity depended on both].

and to Jesus, the Mediator of a new covenant [uniting God and man], and to the sprinkled blood, which speaks [of mercy], a better and nobler and more gracious message than the blood of Abel [which cried out for vengeance].