Augustine of Hippo

Christ Jesus, himself man, is the true Mediator, for, inasmuch as he took the "form of a slave," he became "the Mediator between God and men." In his character as God, he received sacrifices in union with the Father, with whom he is one God. Yet he chose, in his character as a slave, to be himself the sacrifice rather than to receive it, lest any one might take occasion to think that sacrifice could be rendered to a creature. Thus it is that he is both the Priest who offers and the Oblation that is offered.