A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
isa 64:1TRANSITION FROM COMPLAINT TO PRAYER. (Isa 64:1-12)
rend . . . heavens--bursting forth to execute vengeance, suddenly descending on Thy people's foe (Psa 18:9; Psa 144:5; Hab 3:5-6).
flow down-- (Jdg 5:5; Mic 1:4).
isa 64:2Oh, that Thy wrath would consume Thy foes as the fire. Rather, "as the fire burneth the dry brushwood" [GESENIUS].
isa 64:3When--Supply from Isa 64:2, "As when."
terrible things-- (Psa 65:5).
we looked not for--far exceeding the expectation of any of our nation; unparalleled before (Exo 34:10; Psa 68:8).
camest down--on Mount Sinai.
mountains flowed--Repeated from Isa 64:1; they pray God to do the very same things for Israel now as in former ages. GESENIUS, instead of "flowed" here, and "flow" in Isa 64:1, translates from a different Hebrew root, "quake . . . quaked"; but "fire" melts and causes to flow, rather than to quake (Isa 64:2).
isa 64:4perceived by the ear--Paul (Co1 2:9) has for this, "nor have entered into the heart of man"; the virtual sense, sanctioned by his inspired authority; men might hear with the outward ear, but they could only by the Spirit "perceive" with the "heart" the spiritual significancy of God's acts, both those in relation to Israel, primarily referred to here, and those relating to the Gospel secondarily, which Paul refers to.
O God . . . what he . . . prepared--rather, "nor hath eye seen a god beside thee who doeth such things." They refer to God's past marvellous acts in behalf of Israel as a plea for His now interposing for His people; but the Spirit, as Paul by inspiration shows, contemplated further God's revelation in the Gospel, which abounds in marvellous paradoxes never before heard of by carnal ear, not to be understood by mere human sagacity, and when foretold by the prophets not fully perceived or credited; and even after the manifestation of Christ not to be understood save through the inward teaching of the Holy Ghost. These are partly past and present, and partly future; therefore Paul substitutes "prepared" for "doeth," though his context shows he includes all three. For "waiteth" he has "love Him"; godly waiting on Him must flow from love, and not mere fear.
isa 64:5meetest--that is, Thou makest peace, or enterest into covenant with him (see on Isa 47:3).
rejoiceth and worketh--that is, who with joyful willingness worketh [GESENIUS] (Act 10:35; Joh 7:17).
those--Thou meetest "those," in apposition to "him" who represents a class whose characteristics "those that," &c., more fully describes.
remember thee in thy ways-- (Isa 26:8).
sinned--literally, "tripped," carrying on the figure in "ways."
in those is continuance--a plea to deprecate the continuance of God's wrath; it is not in Thy wrath that there is continuance (Isa 54:7-8; Psa 30:5; Psa 103:9), but in Thy ways ("those"), namely, of covenant mercy to Thy people (Mic 7:18-20; Mal 3:6); on the strength of the everlasting continuance of His covenant they infer by faith, "we shall be saved." God "remembered" for them His covenant (Psa 106:45), though they often "remembered not" Him (Psa 78:42). CASTELLIO translates, "we have sinned for long in them ('thy ways'), and could we then be saved?" But they hardly would use such a plea when their very object was to be saved.
isa 64:6unclean thing--legally unclean, as a leper. True of Israel, everywhere now cut off by unbelief and by God's judgments from the congregation of the saints.
righteousness--plural, "uncleanness" extended to every particular act of theirs, even to their prayers and praises. True of the best doings of the unregenerate (Phi 3:6-8; Tit 1:15; Heb 11:6).
filthy rags--literally, a "menstruous rag" (Lev 15:33; Lev 20:18; Lam 1:17).
fade . . . leaf-- (Psa 90:5-6).
isa 64:7stirreth--rouseth himself from spiritual drowsiness.
take hold-- (Isa 27:5).
isa 64:8father-- (Isa 63:16).
clay . . . potter-- (Isa 29:16; Isa 45:9). Unable to mould themselves aright, they beg the sovereign will of God to mould them unto salvation, even as He made them at the first, and is their "Father."
isa 64:9(Psa 74:1-2).
we are . . . thy people-- (Jer 14:9, Jer 14:21).
isa 64:10holy cities--No city but Jerusalem is called "the holy city" (Isa 48:2; Isa 52:1); the plural, therefore, refers to the upper and the lower parts of the same city Jerusalem [VITRINGA]; or all Judea was holy to God, so its cities were deemed "holy" [MAURER]. But the parallelism favors VITRINGA. Zion and Jerusalem (the one city) answering to "holy cities."
isa 64:11house--the temple.
beautiful--includes the idea of glorious (Mar 13:1; Act 3:2).
burned-- (Psa 74:7; Lam 2:7; Ch2 36:19). Its destruction under Nebuchadnezzar prefigured that under Titus.
pleasant things--Hebrew, "objects of desire"; our homes, our city, and all its dear associations.
isa 64:12for these things--Wilt Thou, notwithstanding these calamities of Thy people, still refuse Thy aid (Isa 42:14)?
In Isa 64:9, their plea was, "we are all Thy people." In answer, God declares that others (Gentiles) would be taken into covenant with Him, while His ancient people would be rejected. The Jews were slow to believe this; hence Paul says (Rom 10:20) that Isaiah was "very bold" in advancing so unpopular a sentiment; he implies what Paul states (Rom 2:28; Rom 9:6-7; Rom. 11:1-31), that "they are not all (in opposition to the Jews' plea, Isa 64:9) Israel which are of Israel." God's reason for so severely dealing with Israel is not changeableness in Him, but sin in them (Isa 65:2-7). Yet the whole nation shall not be destroyed, but only the wicked; a remnant shall be saved (Isa 65:8-16). There shall be, finally, universal blessedness to Israel, such as they had prayed for (Isa 65:17-25).