Giobbe 16:21

O that one might plead for a man with God, as a man [pleadeth] for his neighbour!

Ver. 21. O that one might plead for a man with God] Heb. And he will plead for a man with God, and the Son of man for his friend; that is (say our late learned annotators, to whom we are greatly bound for this most sweet and spiritual exposition of the words), Christ, who is God and man, will plead my cause with his Father; he can prevail, because he is God equal to the Father; he will undertake it, because he will be man like to me.

This interpretation agreeth best with the coherence and the words following. And it seemeth that Job knew the mystery of Christ's incarnation, Giobbe 19:25,27, where he speaketh of him both as God, and as a visible Redeemer. Christ is frequently called the Son of man in the New Testament, and believers are called his friends, Giovanni 15:13,15.

By this text thus expounded we see that the doctrine of a mediator between God and man was known and believed in the world long before Christ came into the world. He is the Lamb of God slain from the foundation of the world, Apocalisse 13:8, and to the Jews the ceremonial law was instead of a gospel.