And the head of Ephraim is Samaria, and the head of Samaria is Remaliah's son. If you will not believe, surely you shall not be established.
All Commentaries on Isaiah 7:9 Go To Isaiah 7
Eusebius of Caesarea
AD 339
It is essential to notice that the statement means that those who read it do not only need understanding but also faith; and not only faith but also understanding. Those of the circumcision who do not believe in the Christ of God, though even now they hear these words, do not have understanding of the subject of this prophecy because they do not hear with the mind. The only reason for their lack of understanding is their lack of faith, as the prophecy clearly reveals both about them and to them.