2. The Argument of the book set forth in the words of Athanasius and Jerome. It is an ἀμαλθείας κέρας, horn of plenty.
Saint Athanasius in his Synopsi thus fixes the Argument of this Prophecy in a few words: Τὸ πλεῖστον τῆς προφητείας αὐτοῦ, ἐστιν εὐαγγελία περὶ τῆς ἐνσάρκου παρουσίας τοῦ λόγου τοῦ Θεοῦ, καὶ ὧν ἀνεδέξατο δι᾽ ἡμῶν, παθῶν, the largest part of this Prophecy is the Gospel concerning the coming of the Word of GOD in the flesh, and concerning His sufferings, which He undertook for our sake. He also prophesied against the nations, namely, Babylon, the Philistines, and Damascus. He saw a vision against Egypt, against Tyre, and against the beasts of the wilderness. He also sets forth the Exodus of Sennacherib, and the arrogance of Rabshakeh, and the fall and perdition of both. Moreover, he narrates the sickness of Hezekiah, how he, being about to die, prayed to GOD. He also prophesied concerning Eunuchs and the Gentiles, even in the end, and concerning the day of judgment. Neither shall it be any grief to hear Saint Jerome, Præfatione Commentarii in Esajam, concerning the argument of this prophecy. Now, thus he speaks: Let no one think that I wish to comprehend the argument of this scroll in a brief word, since the Scripture at hand contains the whole Sacred Deposit of the Lord, even as He is preached as Immanuel, born of the virgin, the fulfiller of illustrious works and signs, dead and buried, and rising again from the grave, and Savior of all nations. What shall I say concerning Physics, Ethics, and Logic? Whatever belongs to the holy Scriptures, whatever the human tongue is able to set forth, and the sense of mortals to receive, is contained in that scroll. Hitherto Jerome. To which I add this one thing, that this book includes all sorts of Prophecies, pertaining to the Law and Gospel, to all sorts of doctrines, corrections, exhortations, reproofs, and consolations, and so is, and with good reason is able to be called, an altogether genuine κέρας ἀμαλθείας, horn of plenty.
Dr. Dilday's Lecture: "Isaiah: The Fifth Gospel"