Edward Polhill had the advantage of writing late in the Puritan era. He is extremely well read and is able to cite a variety of previous doctors, as well as bring various positions together into harmony. He has much to say about double justification.
In his book A View of Some Divine Truths, he writes:
Thirdly, Obedience is necessary, though not to the first entrance into justification, yet to the continuance of it; not indeed as a cause, but as a condition. Thus Bishop Davenant, Bona opera sunt necessaria ad justificationis statum retinendum et conservandum; non ut causae, quae per se efficiant aut mereantur hanc conservationem; sed ut media seu conditiones, sine quibus Deus non vult justificationis gratiam in hominibus conservare. If a believer, who is instantly justified upon believing, would continue justified, he must sincerely obey God. Though his obedience in measure and degree reach not fully to the precept of the gospel; yet in truth and substance it comes up to the condition of it; else he cannot continue justified; this to me is very evident; we are at first justified by a living faith, such as virtually is obedience; and cannot continue justified by a dead one such as operates not at all. We are at first justified by a faith which accepts Christ as a Saviour and Lord; and cannot continue justified by such a faith as would divide Christ, taking his salvation from guilt, and by disobedience casting off his lordship; could we suppose that which never comes to pass, that a believer should not sincerely obey: How should he continue justified? if he continue justified, he must, as all justified persons have, needs have a right to life eternal; and if he have such a right, how can he be judged according to his works? no good works being found in him after his believing, how can he be adjudged to life? or how to death, if he continue justified? These things evince, that obedience is a condition necessary as to our continuance in a state of justification: nevertheless it is not necessary, that obedience should be perfect as to the evangelical precept; but that it should be such, that the truth of grace which the evangelical condition calls for, may not fail for want of it: “Blessed are they that do his commandments, that they may have right to the tree of life, and may enter in through the gates into the city,” (Rev. xxii.14.) The first fundamental right to heaven they have by the faith of Christ only: but sincere obedience is necessary that that right may be continued to them: in this sense we may fairly construe that conclusion of St James, “Ye see, then, how that by works a man is justified, and not by faith only,” (Jam. ii.24.) Faith brings a man into a justified estate; but may he rest here? No, his good works must be a proof of his faith, and give a kind of experiment of the life of it. Nay, they are the evangelical condition, upon which his blessed estate of justification is continued to him; in foro legis, Christ and his righteousness is all; neither our faith nor our works can supply the room of his satisfaction to justify against us against the law: but in foro gratiae, our obedience answers to the evangelical condition, and is a means to continue our justified estate: it is true, St. Paul asserts that we are justified by faith, not by works, (Rom iv.); which seems directly contrary to that of St. James, that a man is justified by works, not by faith only. But the difference is reconciled very fairly, if we do but consider what the works are in St. Paul, and what they are in St. James. In St. Paul, the works are pefect works, such as correspond to the law, such as make the reward to be of debt, (ver. 4.) Hence Calvin saith, “Operantem vocat, qui suis meritis aliqui promeretur, non operantem, cui nihil debetar operum merito.” In St. James, the works are sincere only, such as answer not to the law, but to the evangelical condition; such as merit not, but are rewarded out of grace. Works in St. Paul, are such as stand in competition or co-ordination with Christ and his righteousness, which satisfied the law for us. Works in St. James are such as stand in due subordination to Christ and his righteousness, and are required only as fruits of faith, and conditions upon which we are to continue in a justified state.
~A View of Some Divine Truths 1844 ed. in The Works of Edward Polhill soli deo Gloria. 1998 pg. 92-93
In another treatise called Precious Faith, Polhill says more:
There is a double justification; constitutive justification, whereby God maketh us just in this life; sentential justification, whereby God pronounces us just at death and judgment. Constitutive justification is the foundation of sentential, for the true God will not pronounce us just unless we are such; and sentential justification is the completure of constitutive: for here there is sentential judicis, crowning us as righteous; the query, then, being touching constitutive justification in this life, I conceive, with worthy Mr. Baxter, that “God justifies a believer by the moral agency of the gospel, by which, as b his grand charter and law of grace, he doth make over Christ and his righteousness to the believer:” neither need this seem strange, every human instrument doth, moraliter agere. A princes’ pardon conveys an impunity; a charter, an estate; a law, a title or right; a testament, a legacy; and shall not the gospel do as much to believers? God doth constitutive justify the believer by making him righteous, and makes him righteous by making over to him the righteousness of Christ, and that he makes over by the gospel, which is his pardon, charter, law, and testament of grace, conveying the same upon believing: no sooner doth a man believe, but the conditional promise becomes absolute. As the old covenant running, Do this and live, would have justified upon perfect obedience; so the new, running, Believe and be saved, doth justify upon believing; as man sinning is condemned by the law of works, so man believing is justified by the law of grace. Hence the gospel is called, The ministration of righteousness, as the law is of condemnation, (2 Cor. iii. 9); “The power of God to salvation to the believer,” (Rom. i. 16); quia nos per evangelium justificant Deus, because God justifies us by the gospel, as reverend Calvin hath it on the 17th verse; virga virtutis, a rod of strength (Psalm cx. 2), that is, in the justification of men, saith the excellent Dr. Reynolds; and the law of the Spirit of life in Christ Jesus, making us free form the law of sin and death; as many divines interpret that place (Rom viii.2.) Upon which Pareus doth observe, Liberatio a condemnatione legis, Deo, Christo, Evangelio tribuitur; De out authori, Christ out Mediatori, Evangelio ut organo: Freedom from the condemnation of the law, is attributed to God as the author, to Christ as the mediator, to the gospel as the instrument. God makes over Christ and his righteousness unto the believer by the gospel, as by his charter and law of grace. This is the transient act by which God doth justify us in this life.
~ Precious Faith Chapt. VII in The Works of Edward Polhill. (Morgan, PA: Soli Deo Gloria, 1998) 264-265.
Later in the same treatise he addresses the final judgment:
Such reviving refrigerations believers have sometimes here; much more transcendant will their divine refreshments be at the last day. The top-stone of justification shall be then laid on to make it complete, as may appear by the ensuing considerations.
First, Here the believer is justified privately by the gospel, but then he shall be justified openly by the solemn sentence of God before all the world; here he hath the white-stone of absolution given in secret, but then it shall be brought forth to view, glittering in all the orient colours of free-grace. It was a great honour done to Mordecai, to be arrayed in royal apparel, and to have it proclaimed before him, Thus shall it be done to the man whom the king delighteth to honour. But oh! What glory will be upon the believer at that day; when he shall stand in the glorious righteousness of Christ, and hear it proclaimed before men and angels, This is a righteous man; when Christ shall confess him before his Father and the holy angels, to be a piece of himself, of his flesh and of his bones? As it was with the sons of Jesse passing before Samuel; Eliah came and was refused, Abinadab came and was refused, and so others; at last David came, and the Lord said, “Arise, anoint him, for this is he,” (1 Sam. xvi.) So it will be with the sons of men, at the great day of judgment. The great potentate may come and be rejected as a vile person; the rich Dives may come and be put away as dross; the learned rabbi may come, and be turned off as a fool; only when the believer comes, God will say, This is he; this must reign in glory for ever. This is a justification before God after a most signal manner.
Secondly, Here the believer stands justified, but, in the midst of briers and thorns, remaining corruptions vex and tear his righteous soul from day to day. He is in the land of promise, but the Canaanite is not quite drive out; the relics of sin, inmates in the same heart with grace, like the liers in wait for Samson, are ready to make an assault upon him. Hence the Jewish doctors say, That God calls no man saint, or holy, till he be dead an in the grave; because the concupiscential frame is not quite out of him before death, but at that day there shall be nihil damnabile remaining in him. Sin shall be no more: no more tumours of pride; no more boiling up of concupiscence; no more spots or wrinkles, or dark shades of infirmity; nothing but pure spotless holiness: insomuch that divines say, that from henceforth our justification shall be in another way than by imputed righteousness; because, having perfect inherent righteousness in ourselves, we shall need no covering. If the apostle say of a believer, that dedikaiwtai, he is justified from his sins, in respect of sanctification begun, (Rom. vi. 7); how much more will it be true when sin shall be no more.
Thirdly, Here the believer is justified, but the dust of mortality hangs about him. It may be, there is a stone ready to drop into the bladder, or an imposthume ready to break in the head; Mors latet in mediis abdita visceribus, in one part of the body or other death is preparing his arrow upon the string, to shoot man down from the perch of this life into the grave. But at that day there shall be nihil corruptible, death shall be no more; diseases, which use to sound an alarm to it, shall be utterly removed; tears, which are nature’s pay to sorrows, shall be all wiped off; the corruptible shall put on incorruption; mortality shall be swallowed up of life. This is a day of redemption indeed!
Fourthly, Here the believer is justified, but his comfort is not always the same. Now the light of God’s countenance breaks out like a clear sun upon him, and anon there is a sad eclipse, leaving him in darkness; one day a banquet of heavenly comforts is let down into his heart; and another, all is drawn up into heaven again. His evidences may be blurred; Satan may hold up his pardoned sins, as it were in their old guilt; the arrows of God may stick fast in him, and bring qualms and sick-fits upon his conscience: but at that day his comforts shall be unvairable; a nightless day, and a cloudless horizon; an eternal feast upon God and all things in him; his evidences all clear, and, after but this once shewing forth, an everlasting possession o the expected happiness. The accuser, Satan, shall be struck dumb at the blessed sentence of pardon and acceptance pronounced by God before men and angels. God shall never frown, or wound him any more, but wrap him up in the arms of endless love and joy. This will be a day of refreshing indeed. (269)
Notice that Polhill cites Davenant, Baxter, Reynolds, and Pareus. He is attempting to give an overview of the breadth of Reformed orthodoxy in his writings.