No one who has earnestly read through the Scriptures can miss the unique role that the prophet Isaiah played in the unfolding of redemption in the Old Covenant revelation. There are no Messianic heights that take us so high in the Old Testament as those found in the book of Isaiah (cf. Is. chapters 4, 7, 9, 11, 40-45, 50-54, and 40-60). The exceedingly great judgments that God promised to send on Israel and the nations are met with the exceedingly great mercy and salvation that He promises to the same by virtue of the representative Suffering Servant of the LORD (ch. 53). There is an intensity with which Isaiah speaks of the acts of God. Geerhardus Vos once made the observation that of all the writers of Scripture, Isaiah is most comparable in substance and personality to the apostle Paul. He suggested that "Isaiah is an Old Testament Paul and Paul a New Testament Isaiah." You get something of Paul's admiration of Isaiah from the way that he introduced Isaiah 65:1 in Romans 10:20. He prepares his readers for the quote with the words, "Isaiah was very bold." In short, Paul admired Isaiah's boldness, because God had given Paul the same spirit of boldness. Vos explained this similarity between the two men of God when he wrote:

Isaiah in this respect finds his great New Testament counterpart in the apostle Paul. Notwithstanding the immense difference necessarily created by the modified conditions of time and environment, these two favored servants of God are remarkably alike in the distinctive features of their message. Isaiah is an Old Testament Paul and Paul a New Testament Isaiah. For both, there is the same deep impression of the infinite majesty and absolute sovereignty of Jehovah; the same intense realization of the awfulness of the divine justice and the inexorable nature of its claims; the unworthiness, the helplessness of sinful man; the same insistence upon the exclusive activity of God in the work of saving his people; the same prominence of the idea of faith as the only thing whereby man can appropriate the blessings of salvation; the same abounding truth in the marvelous condescension and overflowing grace of God; the same unlimited and unlimitable faith in the world-embracing character of the divine purpose. Paul seems to have felt something of the congeniality of Isaiah's mind to his own. He quotes from him often and not seldom with that fine spiritual insight which penetrates beyond the surface meaning of a passage into the innermost mind of the author and divines the subtle shade of his momentary thought and feeling. "Isaiah is very bold" (Rom. 10:20), he exclaims with evident appreciation of a noble trait exemplified to a high degree in his own character.1

The following are helpful sermon series on the book of Isaiah: Eric Alexander - Isaiah Ray Ortlund Jr. - Isaiah   1. Geerhardus Vos "A Sermon in Isaiah 57:15" [K:NWTS 3/2 (Sep 1988) 3-19]   Nicholas T. Batzig is the organizing pastor/church planter of New Covenant Presbyterian Church, a PCA church in Richmond Hill, Georgia.