Mediator

one who intervenes between two persons who are at variance, with
a view to reconcile them. This word is not found in the Old
Testament; but the idea it expresses is found in Job 9:33, in
the word "daysman" (q.v.), marg., "umpire."

This word is used in the New Testament to denote simply an
internuncius, an ambassador, one who acts as a medium of
communication between two contracting parties. In this sense
Moses is called a mediator in Gal. 3:19.

Christ is the one and only mediator between God and man (1
Tim. 2:5; Heb. 8:6; 9:15; 12:24). He makes reconciliation
between God and man by his all-perfect atoning sacrifice. Such a
mediator must be at once divine and human, divine, that his
obedience and his sufferings might possess infinite worth, and
that he might possess infinite wisdom and knowlege and power to
direct all things in the kingdoms of providence and grace which
are committed to his hands (Matt. 28:18; John 5:22, 25, 26, 27);
and human, that in his work he might represent man, and be
capable of rendering obedience to the law and satisfying the
claims of justice (Heb. 2:17, 18; 4:15, 16), and that in his
glorified humanity he might be the head of a glorified Church
(Rom. 8:29).

This office involves the three functions of prophet, priest,
and king, all of which are discharged by Christ both in his
estate of humiliation and exaltation. These functions are so
inherent in the one office that the quality appertaining to each
gives character to every mediatorial act. They are never
separated in the exercise of the office of mediator.