Isaiah 9:2-7 has been chosen for Christmas Eve because of its the theme of light shining in the darkness (v. 2) and its reference to a child "born for us" who will usher in justice and righteousness "from this time forward and for evermore" (v. 7).
In addition, the angelic announcement in Luke 2:11 may be an allusion to verse 6. The significance of this passage in traditional Christian theology has been immortalized in the words of "For Unto Us a Child is Born" in Handel's Messiah.
Upon consulting the commentaries, however, the would-be preacher is dismayed to learn that this consummate Christmas passage is anything but. One searches in vain for a New Testament reference to these verses, that is, apart from Matthew 4:15-16 which cites verses 1b-2 to explain why godless ("goyische") Galilee became the launching pad for Jesus' ministry. The glorious announcement of verses 6-7, the heart of Handel's Messiah, alas, enjoys no echo in the New Testament.
Rather, the background to our text is found in Isaiah 7:1-9:7. In 734-732 BCE, facing attack from Israel and Syria, Ahaz, the king of Judah, considered enlisting the aid of Assyria. While this would neutralize the threats of his northern neighbors, it would also require entering into alliance with the "Evil Empire" of the day. What should Ahaz do? Isaiah urged Ahaz to stand firm in faith, trust in God, and refuse coalitions with other countries whether it be Syria, Israel or Assyria (Isaiah 7:3-9), thus reassuring the king that God would provide all the protection required and that the birth of a child would serve as a sign of this (Isaiah 7:10-17). Our text announces that significant birth.
In the final form of the book of Isaiah, the material is concentrically arranged: three reasons for the people's joy (C, X, C'; vv. 4-6) form a core framed by poetic descriptions of that joy and the reign of the "child" (B, B'; vv. 2-3, 7a). This poetic material is enclosed by a narrative introduction and conclusion that credit the people's deliverance to Yahweh (A, A'; vv. 1, 7b):
A Narrative intro: "Yahweh" brings judgment and deliverance (v. 1)
B Poetic description of increased joy; "multiplied" (rabah, vv. 2-3)
C Reason 1: Oppression broken; "his shoulders" (shikmo, v. 4)
X Reason 2: Weapons destroyed (v. 5)
C' Reason 3: A child has been born; "his shoulders" (shikmo, v. 6)
B' Poetic description of the reign; "grow continually" (rabah, v. 7a)
A' Narrative conclusion: Yahweh will do this (v. 7b)
Thus, verse 1 (A) serves as a narrative introduction. The phrase "the land of Zebulun and the land of Naphtali" refers to the region of Israel overrun by Tiglath-Pilesar III and annexed as the Assyrian province of Galilee. Whether or not this is the original setting for the oracle in verses 2-7 is a topic that is vigorously debated. Of interest to us is the implied subject of the verbs "brought into contempt" and "will make glorious"; the "he" is none other than Yahweh! This reminder of divine activity is echoed in the assurance of the narrative conclusion (A') where it is emphatically stated that "The zeal of the LORD of hosts will do this" (v. 7b). The dramatic effect of this intentional delay is striking and forms a suitable theological inclusio for the passage as a whole.
The first section of the hymn (vv. 2-3) modulates into a poetic description of the joy that the people have received (or "will receive," the verb tense is disputed; B). The contrasts initiated in the introduction ("former time/latter time") continue here: two descriptions of darkness contrasted with light and resulting in increased joy likened to the delight experienced at the harvest or following victory in war. "You have multiplied" (hirbiyta, v.3) echoes the obscure "grow continually" (lemarbeh, where the "m" is the final form of the letter!) in verse 7a through their derivation from the root rabah, linking B and B' and framing the central section of the hymn.
The central section of the hymn (vv. 4-6) consists of three reasons for the joy just described, each of which begins with the word "for" (ki).
In preaching this text, one should not be put off by the lack of explicit "fulfillment" in the New Testament. Isaiah 7:1--9:7 relates God's coming to us in the birth of a child who will become a sign of God's presence among us ("Immanuel: God with us"). Historically, this may have been Hezekiah. When the New Testament points to Jesus as this child (Matthew 1:23; Isaiah 7:14) or when Handel declares the same with regard to Isaiah 9:6, they are expressing their belief that Jesus is the fulfillment of this divine intention. Isaiah was not looking forward to Jesus; how could the birth of Jesus be a sign to Ahaz? Matthew and Handel mean to say that this is the way God acts--through things as simple as the birth of a child--this is how God fulfills his gracious purpose for us. As Isaiah says, "The zeal of the Lord of hosts will do this!" (9:7b).