The verse contrasts those who “are walking” (a participle) in darkness with those who “will see” (not “have seen” as in NIV) a light of hope in the future. At this point the light is not identified, but it was certainly a sign of hope and deliverance from the darkness that pervaded the land. This light was a sign that God had not completely given up on his people.

Two illustrations of wild celebrative joy are used to compare the people’s future happiness. The people will rejoice and jump for joy like people do when they see an unusually massive harvest (possibly referring to the joy at the Feast of Weeks; Deut 16:9–12) or when they observe the hoards of goods brought home by the troops after an enemy nation is plundered

The yoke, bar, and rod (used of Assyria’s oppression in 10:24–27) were instruments used to dominate people and force them to work physically, or they could be used as metaphors to describe a heavy burden put on people through increased taxation or domineering rule

Although this may usher in a time of peace without war (as in 2:4), the focus of this promise is simply on the utter defeat of the enemy. There is no prediction concerning when in the future this will happen.

This positive oracle comes to a climactic end by announcing the birth of a son who would reign forever as a righteous Davidic ruler (one very different from Ahaz)

Since God is the source of all miraculous events and his plans are the wisest counsel to follow, God will work in and through this son to demonstrate his extraordinary wisdom to plan wonderful miraculous things.

the later use of this same name to describe God himself in 10:21 demands that this son be identified with God in a very close manner. No other person ever has God’s name and God is never called Moses, Abram, David, or Jeremiah, so there must be something very special about this son that causes him to have God’s name

Since fathers were the heads of tribes who wisely led the people, it is a fitting title for a ruler if one wants to avoid some of the negative connotations of kingship. “Everlasting” is a title that does not apply to any human ruler, except that the Davidic promise speaks of one who will rule on the throne of David forever

Peace implies an end of war and is reminiscent of the ideal peace described in the kingdom of God

Finally, Isaiah offers a rhetorical assurance to his listeners concerning the fulfillment of this promise. Simply stated, God Almighty himself will do it. With unassailable zeal, determination, and passion God will concentrate his efforts to accomplish this marvelous deed. Isaiah’s listeners can be absolutely sure that an omnipotent, sovereign God will stand behind the fulfillment of this wonderful plan

The answer to anxiety is the peace of God. Paul made three statements about this peace. First, it is divine peace. He did not envision a situation where circumstances changed or external needs were met. This peace was a characteristic of God which invaded the Christian. Second, it “transcends all understanding.” “Transcends” translates the word hyperechousa (“excellent”), which is found in 2:3; 3:8, and here in a compound form. Paul contrasted knowledge and peace at one point: Peace excels over knowledge. No doubt he had in mind situations where knowledge is insufficient. Sometimes it cannot explain, and sometimes explanations do not help. Peace, however, is always appropriate and meets the need of the heart. Finally, this peace will “guard your hearts and your minds in Christ Jesus.” “Guard” is a military term, implying that peace stands on duty to keep out anything that brings care and anxiety. For these reasons, prayerful people are peaceful people

seek the well-being of others and obtain the same for themselves

Though this shaking (the movement of the mountains) may seem almost unimaginable, it is far more unimaginable for anything to cause God’s “steadfast loving-kindness” (ḥesed, as in vs. 8) to “depart, move” (using the same verb used of the mountains above) from his people. Equally firm is God’s absolute commitment to “my covenant of peace” which will not “shake, totter” (using the same verb used of the hills above). This is a covenant that is even surer than Noah’s everlasting covenant, but the full import of this covenant is not explained. J. Muilenburg suggests that this covenant of peace is related to the peace that the death of the servant mediates

This closing word with peace is like a rainbow arch over the Psalm. The beginning of the Psalm shows us heaven open …; while its close shows us his victorious people upon earth, blessed with peace in the midst of the terrible utterance of his wrath