Biblical Commentary on the Old Testament, by Carl Friedrich Keil and Franz Delitzsh, [1857-78], at sacred-texts.com
As Israel, when redeemed from Egypt beyond the Red Sea, sang songs of praise, so also will the Israel of the second redemption, when brought, in a no less miraculous manner, across the Red Sea and the Euphrates. "And in that day thou wilt say, I thank Thee, O Jehovah, that Thou wast angry with me: Thine anger is turned away, and Thou hast comforted me. Behold, the God of my salvation; I trust, and am not afraid: for Jah Jehovah is my pride and song, and He became my salvation." The words are addressed to the people of the future in the people of the prophet's own time. They give thanks for the wrath experienced, inasmuch as it was followed by all the richer consolation. The formation of the sentence after כּי is paratactic; the principal tone falls upon 1b, where yâshōb is written poetically for vayyâshob (cf., Deu 32:8, Deu 32:18; Psa 18:12; Hos 6:1). We hear the notes of Psa 90:13; Psa 27:1, resounding here; whilst Isa 12:2 is the echo of Exo 15:2 (on which Psa 118:14 is also founded). עזי (to be read ‛ozzi, and therefore also written עזי) is another form of עזּי, and is used here to signify the proud self-consciousness associated with the possession of power: pride, and the expression of it, viz., boasting. Zimrath is equivalent in sense, and probably also in form, to zimrâti, just as in Syriac zemori (my song) is regularly pronounced zemōr, with the i of the suffix dropped (see Hupfeld on Psa 16:6). It is also possible, however, that it may be only an expansion of the primary form zimrath = zimrâh, and therefore that zimrath is only synonymous with zimrâti, as chēphetz in Sa2 23:5 is with chephtzi. One thing peculiar to this echo of Exo 15:2 is the doubling of the Jah in Jâh Jehōvâh, which answers to the surpassing of the type by the antitype.
Isa 12:3, again, contains a prophetic promise, which points back to the commencement of Isa 12:1 : "And with rapture ye will draw water out of the wells of salvation." Just as Israel was miraculously supplied with water in the desert, so will the God of salvation, who has become your salvation, open many and manifold sources of salvation for you (מעיני as it is pointed here, instead of מעיני,
(Note: The root is the same as, for example, in יעלתסּו (they rejoice) and יעלתסּו; here, however, it is more striking, because the singular is written מעין, and not מעין. At the same time, it is evident that the connecting sound ay was rather preferred than avoided, as Ewald maintains - as we may see, for example, from the repeated aychi in Ps 103.))
from which ye may draw with and according to your heart's delight. This water of salvation, then, forms both the material for, and instigation to, new songs of praise; and Isa 12:4-6 therefore continue in the strain of a psalm: "And ye will say in that day, Praise Jehovah, proclaim His name, make known His doings among the nations, boast that His name is exalted. Harp to Jehovah; for He has displayed majesty: let this be known in all lands. Shout and be jubilant, O inhabitants of Zion: for great is the Holy One of Israel in the midst of thee." The first song of six lines is here followed by a second of seven lines: a prophetic word of promise, inserted between them, separates the one from the other. This second also commences with the well-known tones of a psalm (compare especially Psa 105:1; Ch1 16:8). The phrase, "Call upon the name of Jehovah," signifies, Make the name of Jehovah the medium of invocation (Ges. 138, Anm. 3*), i.e., invoke it, or, as here, call it out. Gē'ūth is high, towering dignity; here it is used of God, as in Isa 26:10, with ‛âsâh: to prove it practically, just as with lābēsh in Psa 93:1, to show one's self openly therein. Instead of the Chethib meyudda‛ath in Isa 12:5, the keri substitutes the hophal form mūda‛ath, probably because meyuddâ‛, according to the standing usage of speech, denotes one well known, or intimate; the passive of the hophal is certainly the more suitable. According to the preceding appeals, the words are to be understood as expressing a desire, that the glorious self-attestation of the God of salvation might be brought to the consciousness of the whole of the inhabitants of the earth, i.e., of all mankind. When God redeems His people, He has the salvation of all the nations in view. It is the knowledge of the Holy One of Israel, made known through the word of proclamation, that brings salvation to them all. How well may the church on Zion rejoice, to have such a God dwelling in the midst of it! He is great as the giver or promises, and great in fulfilling them; great in grace, and great in judgment; great in all His saving acts which spread from Israel to all mankind. Thus does this second psalm of the redeemed nation close, and with it the book of Immanuel.