The following is from The Doctrine of Justification by Arthur Pink:

Its Source

Let us here review, briefly, the ground which we have already covered. We have seen, first, that "to justify" means to pronounce righteous. It is not a divine work, but a divine verdict, the sentence of the Supreme Court, declaring that the one justified stands perfectly conformed to all the requirements of the law. Justification assures the believer that the Judge of all the earth is for him, and not against him: that justice itself is on his side. Second, we dwelt upon the great and seemingly insolvable problem which is thereby involved: how a God of truth can pronounce righteous one who is completely devoid of righteousness, how He can receive into His judicial favor one who is a guilty criminal, how He can exercise mercy without insulting justice, how He can be gracious and yet enforce the high demands of His law. Third, we have shown that the solution to this problem is found in the perfect satisfaction which the incarnate Son rendered unto divine law, and that on the basis of that satisfaction God can truthfully and righteously pronounce just all who truly believe the gospel. In our last chapter we pointed out that the satisfaction which Christ made to the divine law consists of two distinct parts, answering to the twofold need of him who is to be justified. First, as a responsible creature I am under binding obligations to keep the law—to love God with all my heart and my neighbor as myself. Second, as a criminal I am under the condemnation and curse of that law which I have constantly transgressed in thought and word and deed. Therefore, if another was to act as my surety and make reparation for me, he must perfectly obey all the precepts of the law, and then endure the awful penalty of the law. That is exactly what was undertaken and accomplished by the Lord Jesus in His virtuous life and vicarious death. By Him every demand of the law was fulfilled; by Him every obligation of the believer was fully met. It has been objected by some that the obedience of Christ could not be imputed to the account of others, for being "made under the law" (Galatians 4:4) as man, He owed submission to the law on His own account. This is a serious mistake, arising out of a failure to recognize the absolute uniqueness of the Man Christ Jesus. Unlike us, He was never placed under the Adamic Covenant, and therefore He owed nothing to the law. Moreover, the manhood of Christ never had a separate existence: in the virgin's womb the eternal Son took the seed of Mary into union with His Deity, so that whereas the first man was of the earth, earthy, "the second Man is the Lord from Heaven" (1 Corinthians 15:47), and as such He was infinitely superior to the law, owing nothing to it, being personally possessed of all the excellencies of Deity. Even while He walked this earth "in Him dwells all the fullness of the Godhead bodily." It was entirely for His peoples' sake that the God-man Mediator was "made under the law." It was in order to work out for them a perfect righteousness, which should be placed to their account, that He took upon Himself the form of a servant and became "obedient unto death." What has been said above supplies the answer to another foolish objection which has been made against this blessed truth, namely, that if the obedience of the Man Christ Jesus were transferable it would be available only for one other man, seeing that every human being is required to obey the law, and that if vicarious obedience be acceptable to God then there would have to be as many separate sureties as there are believers who are saved. That would be true if the "surety" were merely human, but inasmuch as the Surety provided by God is the God-man Mediator, His righteousness is of infinite value, for the law was more "honored and magnified" by the obedience of "the Lord from Heaven" than had every member of the human race perfectly kept it. The righteousness of the God-man Mediator is of infinite value, and therefore available for as many as God is pleased to impute it unto. The value or merit of an action increases in proportion to the dignity of the person who performs it, and He who obeyed in the room and stead of the believer was not only a holy man, but the Son of the living God. Moreover, let it be steadily borne in mind that the obedience which Christ rendered to the law was entirely voluntary. Prior to His incarnation, He was under no obligation to the law, for He had Himself (being God) formulated that law. His being made of a woman and made under the law was entirely a free act on His own part. We come into being and are placed under the law without our consent; but the Lord from Heaven existed before His incarnation, and assumed our nature by His spontaneous act: "Lo, I come... I delight to do Your will" (Psalm 40:7, 8). No other person could use such language, for it clearly denotes a liberty to act or not to act, which no mere creature possesses. Placing Himself under the law and rendering obedience to it was founded solely on His own voluntary deed. His obedience was therefore a "free will offering," and therefore as He did not owe obedience to the law by any prior obligation, not being at all necessary for Himself, it is available for imputation to others, that they should be rewarded for it. If, then, the reader has been able to follow us closely in the above observations, it should be clear to him that when Scripture speaks of God "justifying the ungodly" the meaning is that the believing sinner is brought into an entirely new relation to the law; that in consequence of Christ's righteousness being made over to him, he is now absolved from all liability to punishment, and is given a title to all the reward merited by Christ's obedience. Blessed, blessed truth for comforting the conscientious Christian who daily groans under a sense of his sad failures and who mourns because of his lack of practical conformity to the image of Christ. Satan is ever ready to harass such an one and tell him his profession is vain. But it is the believer's privilege to overcome him by "the blood of the Lamb" (Rev. 12:11)—to remind himself anew that Another has atoned for all his sins, and that despite his innumerable shortcomings he still stands "accepted in the Beloved" (Ephesians 1:6). If I am truly resting on the finished work of Christ for me, the Devil cannot successfully lay anything to my charge before God, though if I am walking carelessly He will suffer him to charge my conscience with unrepented and unconfessed sins. In the last chapter, under the nature of justification, we saw that the constituent elements of this divine blessing are two in number, the one being negative in its character, the other positive. The negative blessing is the cancellation of guilt, or the remission of sins—the entire record of the believer's transgressions of the law, filed upon the divine docket, having been blotted out by the precious blood of Christ. The positive blessing is the bestowal upon the believer of an inalienable title to the reward which the obedience of Christ merited for him— that reward is life, the judicial favor of God, Heaven itself. The unchanging sentence of the law is "the man whio does those things shall live by them" (Romans 10:5). As we read in Romans 7:10, "the commandment, which was ordained to life." It is just as true that obedience to the law secured life, as disobedience insured death. When the young ruler asked Christ "what good thing shall I do, that I may have eternal life?" He answered, "If you will enter into life, keep the commandments" (Matthew 19:16, 17). It was because His people had failed to "keep the commandments" that the God-man Mediator was "made under the law," and obeyed it for them. And therefore its reward of "life" is due unto those whose Surety He was; yes, due unto Christ Himself to bestow upon them. Therefore did the Surety, when declaring "I have glorified You on the earth: I have finished the work which you gave me to do" (John 17:4), remind the Father, "that He should give eternal life to as many as you have given him" (verse 2). But more, on the footing of justice, Christ demands that His people be taken to Heaven, saying, "Father, I will that they also, whom You have given Me, be with Me where I am" (John 17:24)—He claims eternal life for His people on the ground of His finished work, as the reward of His obedience. "Therefore as by the offence of one judgment came upon all men to condemnation; even so by the righteousness of One the free gift came upon all men unto justification of life" (Romans 5:18). The offence of the first Adam brought down the curse of the broken law upon the whole human race; but the satisfaction of the last Adam secured the blessing of the fulfilled law upon all those whom He represented. Judgment unto condemnation is a law term intending eternal death, the wages of sin; the "free gift" affirms that a gratuitous justification is bestowed upon all its recipients—"justification of life" being the issue of the gift, parallel with "shall reign in life by one, Jesus Christ" (verse 17). The sentence of justification adjudges and entitles its object unto eternal life. Having now considered the two great blessings which come to the believer at his justification—deliverance from the curse of the law (death) and a title to the blessing of the law (life)—let us now seek to take a view of the originating source from which they proceed. This is the free, pure sovereign grace of God: as it is written "Being justified freely by His grace" (Romans 3:24). What is grace? It is God's unmerited and uninfluenced favor, shown unto the undeserving and Hell-deserving: neither human worthiness, works or willingness, attracting it, nor the lack of them repelling or obstructing it. What could there be in me to win the favorable regard of Him who is of too pure eyes to behold evil, and move Him to justify me? Nothing whatever; nay, there was everything in me calculated to make Him abhor and destroy me—my very self-righteous efforts to earn a place in Heaven deserving only a lower place in Hell. If, then, I am ever to be "justified" by God it must be by pure grace, and that alone. Grace is the very essence of the gospel—the only hope for fallen men, the sole comfort of saints passing through much tribulation on their way to the kingdom of God. The gospel is the announcement that God is prepared to deal with guilty rebels on the ground of free favor, of pure benignity; that God will blot out sin, cover the believing sinner with a robe of spotless righteousness, and receive him as an accepted son: not on account of anything he has done or ever will do, but of sovereign mercy, acting independently of the sinner's own character and deservings of eternal punishment. Justification is perfectly gratuitous so far as we are concerned, nothing being required of us in order to possess it, either in the way of price and satisfaction or preparation and fitness. We have not the slightest degree of merit to offer as the ground of our acceptance, and therefore if God ever does accept us it must be out of unmingled grace. It is as "the God of all grace" (1 Peter 5:10) that Jehovah justifies the ungodly. It is as "the God of all grace" He seeks, finds, and saves His people: asking them for nothing, giving them everything. Strikingly is this brought out in that word "being justified freely by His grace" (Romans 3:24), the design of that adverb being to exclude all consideration of anything in us or from us which should be the cause or condition of our justification. That same Greek adverb is translated "without a cause" in John 15:25—"they hated Me without a cause." The world's hatred of Christ was "without a cause" so far as He was concerned: there was nothing whatever in Him which, to the slightest degree, deserved their enmity against Him: there was nothing in Him unjust, perverse, or evil; instead, there was everything in Him which was pure, holy, lovely. In like manner, there is nothing whatever in us to call forth the approbation of God: by nature there is "no good thing" in us; but instead, everything that is evil, vile, loathsome. "Being justified without a cause by His GRACE." How this tells out the very heart of God! While there was no motive to move Him, outside of Himself, there was one inside Himself; while there was nothing in us to impel God to justify us, His own grace moved Him, so that He devised a way whereby His wondrous love could have vent and flow forth to the chief of sinners, the vilest of rebels. As it is written, "I, even I, am He who blots out your transgressions for Mine own sake, and will not remember your sins" (Isaiah 43:25). Wondrous, matchless grace! We cannot for a moment look outside the grace of God for any motive or reason why He should ever have noticed us, still less had respect unto such ungodly wretches. The first moving cause, then, that inclined God to show mercy to His people in their undone and lost condition, was His own wondrous grace—unsought, uninfluenced, unmerited by us. He might justly have left us all obnoxious to the curse of His law, without providing any Surety for us, as He did the fallen angels; but such was His grace toward us that "He spared not His own Son." "Not by works of righteousness which we have done, but according to His mercy He saved us, by the washing of regeneration, and renewing of the Holy Spirit; Which He shed on us abundantly through Jesus Christ our Savior; That being justified by His grace, we should be made heirs according to the hope of eternal life" (Titus 3:5-7). It was His own sovereign favor and good will which actuated God to form this wondrous scheme and method of justification. Against what has been said above, it has been objected by Socinians and their echoists that this cannot be: if the believing sinner is justified upon the grounds of a full satisfaction having been made to God for him by a surety, then his discharge from condemnation and his reception into God's judicial favor must be an act of pure justice, and therefore could not be by grace. Or, if it be purely an act of divine grace, then no surety can have obeyed the law in the believer's stead. But this is to confound two distinct things: the relation of God to Christ the Surety, and the relation of God to me the sinner. It was grace which transferred my sins to Christ; it was justice which smote Christ on account of those sins. It was grace which appointed me unto everlasting bliss; it is justice to Christ which requires I shall enjoy that which He purchased for me. Toward the sinner justification is an act of free unmerited favor; but toward Christ, as a sinner's Surety, it is an act of justice that eternal life should be bestowed upon those for whom His meritorious satisfaction was made. First, it was pure grace that God was willing to accept satisfaction from the hands of a surety. He might have exacted the debt from us in our own persons, and then our condition had been equally miserable as that of the fallen angels, for whom no mediator was provided. Second, it was wondrous grace that God Himself provided a Surety for us, which we could not have done. The only creatures who are capable of performing perfect obedience are the holy angels, yet none of them could have assumed and met our obligations, for they are not akin to us, possessing not human nature, and therefore incapable of dying. Even had an angel became incarnate, his obedience to the law could not have availed for the whole of God's elect, for it would not have possessed infinite value. None but a divine person taking human nature into union with Himself could present unto God a satisfaction adequate for the redemption of His people. And it was impossible for men to have found out that Mediator and Surety: it must have its first rise in God, and not from us: it was He who "found" a ransom (Job 33:24) and laid help upon One that is "mighty" (Psalm 89:19). In the last place, it was amazing grace that the Son was willing to perform such a work for us, without whose consent the justice of God could not have exacted the debt from Him. And His grace is the most eminent in that He knew beforehand all the unspeakable humiliation and unparalleled suffering which He would encounter in the discharge of this work, yet that did not deter Him; nor was He unapprized of the character of those for whom He did it—the guilty, the ungodly, the Hell-deserving; yet He shrank not back. "O to grace how great a debtor, Daily I'm constrained to be! Let Your grace, Lord, like a fetter, Bind my wandering heart to Thee."