Unto us a child is born
Whether the promised child is Hezekiah, a later Davidic king, or the Messiah, and how the tenses are read.
Isaiah 9:1-7
1But there shall be no more gloom for her who was in anguish. In the former time, he brought into contempt the land of Zebulun and the land of Naphtali; but in the latter time he has made it glorious, by the way of the sea, beyond the Jordan, Galilee of the nations.
2The people who walked in darkness have seen a great light. The light has shined on those who lived in the land of the shadow of death.
3You have multiplied the nation. You have increased their joy. They rejoice before you according to the joy in harvest, as men rejoice when they divide the plunder.
4For the yoke of his burden, and the staff of his shoulder, the rod of his oppressor, you have broken as in the day of Midian.
5For all the armor of the armed man in the noisy battle, and the garments rolled in blood, will be for burning, fuel for the fire.
6For a child is born to us. A son is given to us; and the government will be on his shoulders. His name will be called Wonderful Counselor, Mighty God, Everlasting Father, Prince of Peace.
7Of the increase of his government and of peace there shall be no end, on David’s throne, and on his kingdom, to establish it, and to uphold it with justice and with righteousness from that time on, even forever. The zeal of Yahweh of Armies will perform this.
What each tradition says
Rabbinic / Midrashic
Rashi says that on the throne of David’s kingdom, this peace will be the justice and righteousness Hezekiah performed. The promised peace is thus connected to Hezekiah’s deeds.
Rashi (trans. A. J. Rosenberg), Rashi on Isaiah (The Judaica Press complete Tanach with Rashi) - Sefaria — Comment on Isaiah 9:6 (and for peace)
Patristic
Novatian reads Isaiah's “unto us a child is born” as spoken of Christ, even though Christ had not yet been born in Isaiah's time. Scripture, he says, announces things not yet done as already done because they certainly shall be; it narrates future events as accomplished rather than predicting them as future.
Novatian, A Treatise of Novatian Concerning the Trinity (ANF vol. 5, trans. H. Moore) — Chapter 28 (on Isa. ix. 6)
Catholic
Haydock says the child is the Messiah, whom Isaiah’s son prefigured. 'Shoulder' is where royal badges were worn; Christ bore his cross. 'Wonderful' refers to his birth; 'Counsellor' is from whom all good advice proceeds. He rejects Grotius’s 'consulter of the strong God' as meaning Hezekiah, who was ten, did not always take advice, and whose reign was not peaceful.
George Haydock (with Calmet, Tertullian, Grotius), George Haydock's Catholic Bible Commentary — Comment on Isaiah 9:6
Orthodox
Cyril of Jerusalem reads Isaiah's words "unto us a child is born, unto us a Son is given" as spoken of us, not of them. He marks the order: He was first the Son of God, and then was given to us.
Cyril of Jerusalem, Catechetical Lectures (NPNF ser. 2 vol. 7, trans. E. H. Gifford) — Lecture XII, sec. 24 (on Isa. ix. 5-6)
Reformed / Protestant
Matthew Henry reads Isaiah 9:6–7 as done by the Messiah, Immanuel, the son of the virgin foretold in Isaiah 7:14. He says the prophet speaks in prophetic style as though already done: the child is born because it was certain, and the church before the incarnation benefited from his undertaking under Genesis 3:15.
Matthew Henry, An Exposition of the Old and New Testament, Vol. IV (Isaiah) — Comment on Isa. ix. 6
Evangelical
Wesley holds that the child’s titles apply to Christ. Christ is the Wonderful Counsellor, who counsels and preserves his church in all ages through apostles and prophets, possessing all wisdom and knowledge. Mighty God can agree to no man but Christ, who is God as well as man.
John Wesley, Wesley's Notes on the Bible, Isaiah (Wesley Center Online) — Chapter IX, note on v. 6 (his name)