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 50:1THE JUDGMENTS ON ISRAEL WERE PROVOKED BY THEIR CRIMES, YET THEY ARE NOT FINALLY CAST OFF BY GOD. (Isa 50:1-11)
Where . . . mothers divorcement--Zion is "the mother"; the Jews are the children; and God the Husband and Father (Isa 54:5; Isa 62:5; Jer 3:14). GESENIUS thinks that God means by the question to deny that He had given "a bill of divorcement" to her, as was often done on slight pretexts by a husband (Deu 24:1), or that He had "sold" His and her "children," as a poor parent sometimes did (Exo 21:7; Kg2 4:1; Neh 5:5) under pressure of his "creditors"; that it was they who sold themselves through their own sins. MAURER explains, "Show the bill of your mother's divorcement, whom . . . ; produce the creditors to whom ye have been sold; so it will be seen that it was not from any caprice of Mine, but through your own fault, your mother has been put away, and you sold" (Isa 52:3). HORSLEY best explains (as the antithesis between "I" and "yourselves" shows, though LOWTH translates, "Ye are sold") I have never given your mother a regular bill of divorcement; I have merely "put her away" for a time, and can, therefore, by right as her husband still take her back on her submission; I have not made you, the children, over to any "creditor" to satisfy a debt; I therefore still have the right of a father over you, and can take you back on repentance, though as rebellious children you have sold yourselves to sin and its penalty (Kg1 21:25).
bill . . . whom--rather, "the bill with which I have put her away" [MAURER].
no man--willing to believe in and obey Me (Isa 52:1, Isa 52:3). The same Divine Person had "come" by His prophets in the Old Testament (appealing to them, but in vain, Jer 7:25-26), who was about to come under the New Testament.
hand shortened--the Oriental emblem of weakness, as the long stretched-out hand is of power (Isa 59:1). Notwithstanding your sins, I can still "redeem" you from your bondage and dispersion.
dry up . . . sea-- (Exo 14:21). The second exodus shall exceed, while it resembles in wonders, the first (Isa 11:11, Isa 11:15; Isa 51:15).
make . . . rivers . . . wilderness--turn the prosperity of Israel's foes into adversity.
fish stinketh--the very judgment inflicted on their Egyptian enemies at the first exodus (Exo 7:18, Exo 7:21).
isa 50:3heavens . . . blackness--another of the judgments on Egypt to be repeated hereafter on the last enemy of God's people (Exo 10:21).
sackcloth-- (Rev 6:12).
isa 50:4Messiah, as "the servant of Jehovah" (Isa 42:1), declares that the office has been assigned to Him of encouraging the "weary" exiles of Israel by "words in season" suited to their case; and that, whatever suffering it is to cost Himself, He does not shrink from it (Isa 50:5-6), for that He knows His cause will triumph at last (Isa 50:7-8).
learned--not in mere human learning, but in divinely taught modes of instruction and eloquence (Isa 49:2; Exo 4:11; Mat 7:28-29; Mat 13:54).
speak a word in season-- (Pro 15:23; Pro 25:11). Literally, "to succor by words," namely, in their season of need, the "weary" dispersed ones of Israel (Deu 28:65-67). Also, the spiritual "weary" (Isa 42:3; Mat 11:28).
wakeneth morning by morning, &c.--Compare "daily rising up early" (Jer 7:25; Mar 1:35). The image is drawn from a master wakening his pupils early for instruction.
wakeneth . . . ear--prepares me for receiving His divine instructions.
as the learned--as one taught by Him. He "learned obedience," experimentally, "by the things which He suffered"; thus gaining that practical learning which adapted Him for "speaking a word in season" to suffering men (Heb 5:8).
isa 50:5opened . . . ear--(See on Isa 42:20; Isa 48:8); that is, hath made me obediently attentive (but MAURER, "hath informed me of my duty"), as a servant to his master (compare Psa 40:6-8, with Phi 2:7; Isa 42:1; Isa 49:3, Isa 49:6; Isa 52:13; Isa 53:11; Mat 20:28; Luk 22:27).
not rebellious--but, on the contrary, most willing to do the Father's will in proclaiming and procuring salvation for man, at the cost of His own sufferings (Heb 10:5-10).
isa 50:6smiters--with scourges and with the open hand (Isa 52:14; Mar 14:65). Literally fulfilled (Mat 27:26; Mat 26:27; Luk 18:33). To "pluck the hair" is the highest insult that can be offered an Oriental (Sa2 10:4; Lam 3:30). "I gave" implies the voluntary nature of His sufferings; His example corresponds to His precept (Mat 5:39).
spitting--To spit in another's presence is an insult in the East, much more on one; most of all in the face (Job 30:10; Mat 27:30; Luk 18:32).
isa 50:7Sample of His not being "discouraged" (Isa 42:4; Isa 49:5).
set . . . face like . . . flint--set Myself resolutely, not to be daunted from My work of love by shame or suffering (Eze 3:8-9).
isa 50:8(Isa 49:4). The believer, by virtue of his oneness with Christ, uses the same language (Psa 138:8; Rom 8:32-34). But "justify" in His case, is God's judicial acceptance and vindication of Him on the ground of His own righteousness (Luk 23:44-47; Rom 1:4; Ti1 3:16, with which compare Pe1 3:18); in their case, on the ground of His righteousness and meritorious death imputed to them (Rom 5:19).
stand together--in judgment, to try the issue.
adversary--literally, "master of my cause," that is, who has real ground of accusation against me, so that he can demand judgment to be given in his favor (compare Zac 3:1, &c. Rev 12:10).
isa 50:9(Compare "deal," or "proper," Isa 52:13, Margin; Isa 53:10; Psa 118:6; Jer 23:5).
as a garment-- (Isa 51:6, Isa 51:8; Psa 102:26). A leading constituent of wealth in the East is change of raiment, which is always liable to the inroads of the moth; hence the frequency of the image in Scripture.
isa 50:10Messiah exhorts the godly after His example (Isa 49:4-5; Isa 42:4) when in circumstances of trial ("darkness," Isa 47:5), to trust in the arm of Jehovah alone.
Who is, &c.--that is, Whosoever (Jdg 7:3).
obeyeth . . . servant--namely, Messiah. The godly "honor the Son, even as they honor the Father" (Joh 5:23).
darkness-- (Mic 7:8-9). God never had a son who was not sometimes in the dark. For even Christ, His only Son, cried out, "My God, My God, why hast Thou forsaken Me?"
light--rather, "splendor"; bright sunshine; for the servant of God is never wholly without "light" [VITRINGA]. A godly man's way may be dark, but his end shall be peace and light. A wicked man's way may be bright, but his end shall be utter darkness (Psa 112:4; Psa 97:11; Psa 37:24).
let him trust in the name of the Lord--as Messiah did (Isa 50:8-9).
isa 50:11In contrast to the godly (Isa 50:10), the wicked, in times of darkness, instead of trusting in God, trust in themselves (kindle a light for themselves to walk by) (Ecc 11:9). The image is continued from Isa 50:10, "darkness"; human devices for salvation (Pro 19:21; Pro 16:9, Pro 16:25) are like the spark that goes out in an instant in darkness (compare Job 18:6; Job 21:17, with Psa 18:28).
sparks--not a steady light, but blazing sparks extinguished in a moment.
walk--not a command, but implying that as surely as they would do so, they should lie down in sorrow (Jer 3:25). In exact proportion to mystic Babylon's previous "glorifying" of herself shall be her sorrow (Mat 25:30; Mat 8:12; Rev 18:7).