ping for comment
Man's justification IS extrinsic to him. He can't accomplish it himself but is declared just by the decree of God.
Colossians 2:13-14 And you, who were dead in your trespasses and the uncircumcision of your flesh, God made alive together with him, having forgiven us all our trespasses, by canceling the record of debt that stood against us with its legal demands. This he set aside, nailing it to the cross.
Man isn't justified because he has a new nature. Yes, he was given a new nature, but the justification is a declaration by God, not a result of anything man can do about it. A dead man cannot do anything. And that passage declares that it's all God's working.
I'm not sure who the author is referencing, but at the risk of contradicting Luther, I would suggest that God's "hidden and awful will" really should be God's "hidden and perfect will". The fact that our God predestined punishment for sinners does not contradict God's love and mercy. It just simply shows us we cannot understand the mind of God and how this is a merciful act. Yet it is. Thus it is best not to speculate but only accept this fact.
Paul actually includes Wisdom books (Psalms, Prov., Eccl.) and prophets as part of the Law, and places everyone under its condemnation.
hat then? are we better [than they]? No, in no wise: for we have before proved both Jews and Gentiles, that they are all under sin; Gal 3:22; 10 As it is written, There is none righteous, no, not one: Ps 14:3; Ps 53:3; 11 There is none that understandeth, there is none that seeketh after God. Ps 53:2; 12 They are all gone out of the way, they are together become unprofitable; there is none that doeth good, no, not one. Eccl. 7:20; Is. 64:6; 13 Their throat [is] an open sepulchre; with their tongues they have used deceit; the poison of asps [is] under their lips: Ps 5:9; Ps 140:3; 14 Whose mouth [is] full of cursing and bitterness: Ps 10:7; 15 Their feet [are] swift to shed blood: Prov 1:16; Isa 59:7; 16 Destruction and misery [are] in their ways: 17 And the way of peace have they not known: 18 There is no fear of God before their eyes. Ps 36:1;
19 Now we know that what things soever the law saith, it saith to them who are under the law: that every mouth may be stopped, and all the world may become guilty before God. 20 Therefore by the deeds of the law there shall no flesh be justified in his sight: for by the law [is] the knowledge of sin. Mt. 5:19; 15:18,19; Mk. 10:18,19; Gal.2:16; Rm.2:20; 7:7; Heb 7:18; 21 But now the righteousness of God without the law is manifested, being witnessed by the law and the prophets; Lk. 24:.27; Rm.1:17; Phil 3:9; 22 Even the righteousness of God [which is] by faith of Jesus Christ unto all and upon all them that believe: for there is no difference: Jn. 1:12,13; 23 For all have sinned, and come short of the glory of God; Mk. 10:18; 24 Being justified freely by his grace through the redemption that is in Christ Jesus: Isa 53:5; 25 Whom God hath set forth [to be] a propitiation through faith in his blood, to declare his righteousness for the remission of sins that are past, through the forbearance of God; Lk. 24:44,47 2Cor 5:19; Col 1:20; Heb 4:16; 1John 4:10; Exod 25:17; 26 To declare, [I say], at this time his righteousness: that he might be just, and the justifier of him which believeth in Jesus. Jn. 1:17; 27 Where [is] boasting then? It is excluded. By what law? of works? Nay: but by the law of faith.
And the law is used because,
"if there had been a law given which could have given life, verily righteousness should have been by the law. (Galatians 3:21)