This Deliverer will also be called the Everlasting Father. Many people are puzzled by this title because the Messiah, God’s Son, is distinguished in the Trinity from God the Father. How can the Son be the Father? Several things must be noted in this regard. First, the Messiah, being the second Person of the Trinity, is in His essence, God. Therefore He has all the attributes of God including eternality. Since God is One (even though He exists in three Persons), the Messiah is God. Second, the title “Everlasting Father” is an idiom used to describe the Messiah’s relationship to time, not His relationship to the other Members of the Trinity. He is said to be everlasting, just as God (the Father) is called “the Ancient of Days” (Dan. 7:9). The Messiah will be a “fatherly” Ruler. Third, perhaps Isaiah had in mind the promise to David (2 Sam. 7:16) about the “foreverness” of the kingdom which God promised would come through David’s line. The Messiah, a Descendant of David, will fulfill this promise for which the nation had been waiting.
Martin, J. A. (1985). Isaiah. In J. F. Walvoord & R. B. Zuck (Eds.), The Bible Knowledge Commentary: An Exposition of the Scriptures (Vol. 1, p. 1053). Wheaton, IL: Victor Books.