There are no loose ends in the implementation of God’s plan. Every last detail has been worked out perfectly and, no matter how hard we scrutinize, we will find no deficiency.
There are two prophecies quoted here, the first from Psalm 2:7, and in the next verse the second from Psalm 110. But someone might ask, in what way does Psalm 2 prove that Christ was appointed a priest, since it does not mention priesthood? This verse has already been quoted in Hebrews 1:5 to establish the incarnation of the Son of God, but now it is used to show that Christ was made our high priest. Before he can become high priest he must be born, for he can only be a priest to men if he shares their nature, and so he took flesh and blood (Hebrews 2:14). But since also there could be no other reason why the Son of God should be made incarnate except to represent his people, then his incarnation implies his priesthood, for he is made incarnate to carry out the work of a priest. The point being made is that he did not appoint himself to be high priest, and so even in the matter of his incarnation which logically came first, Scripture makes clear that this was by the decree of God.