“The grace of our Lord Jesus Christ be with you all.  Amen.”

“The grace of our Lord Jesus Christ”–
This is the conclusion of Tertius’ personal remarks, and is similar to what Paul used above.

It is possible that Tertius wrote verses 22-24, without receiving any particular instructions from Paul, except the bare permission to add his own salutations with those of his particular friends. This is a repetition of the benediction as in verse 20, save that it is here invoked on them “all.”

                        GRACE:  (Grk.–charis)–Spiritual favor from God.

“be with you all.  Amen.”
Literally: {Be} with you all.  Amen.–Here again Paul, from the abundance of his affectionate heart towards them, repeats his benediction to them, that the mercy, grace, and goodness, of the Lord Jesus Christ, may abide upon, and evermore continue with, them.

All commentators agree that the Epistle to the Romans is the foundational doctrinal epistle.  One pastor whom I know has described this Epistle to the Romans as:  The Constitution and Bylaws of the Christian Faith.  A very good definition!  Consequently, the great doctrines of Christianity appear there.  But it is not generally recognized that in verses 25-27 preparation is made by the Apostle Paul for the unfolding in his further epistles of the great secret of God called, “The Mystery;”  that is, the mystery of the church.; that which was kept in silence through the times of ages, the special of which is Paul. This is the only epistle of Paul’s which closes with a doxology.

“Now to Him that is of power to stablish you according to my gospel, and the preaching of Jesus Christ, according to the revelation of the mystery, which was kept secret since the world began.”

“Now to Him”
Literally:  “To the {One}.”–This, and the two following verses, are found in many manuscripts at the close of Chapter 14.  Its proper place, however, is here; and Paul thus concludes the whole epistle with an ascription of praise. Verses 25-27 conclude the noble epistle with the finest of Paul's doxologies.

“that is of power to stablish you”
Literally: {Who is} able to establish you.”–To God, without Whom nothing is wise, nothing strong; Who is as willing to teach as He is wise; as ready to help as He is strong.

          IS OF POWER: | (Grk.–dunamenôi)—Is able; who has power, (Eph. 3:20; Jude 1:24), “Now unto him that is able to keep you from failing,” etc. Only God can keep Christians in the path of salvation; and it was well to bring that truth prominently into view at the close of the epistle.

          STABLISH: (Grk.–stêrizô)—“to make stable, to place firmly, set fast, confirm or uphold.” (See I Pet. 5:10). To strengthen and confirm you.  This word is used some ten times in the N.T. concerning a settled, stable spiritual condition.

“according to my Gospel”–According to the Gospel which I preach; the doctrines which I have been defending in this epistle. That is, in conformity with the truths of that Gospel which I preach, and not I only, but all to whom has been committed “the preaching of Jesus Christ.”

            It is called his Gospel, not because he was the author of it, or because others did not preach it also, but because he had been particularly defending it in this epistle. The doctrines which he had advanced were just those which were fitted to strengthen and confirm them–the doctrine of justification, of election, of perseverance, and of the protection and favor of God to both Jews and Gentiles. These were the doctrines which he had defended; and it might easily be shown that these are the doctrines that give stability to the Christian faith, hope, and love.
          That Gospel which explains and publishes  God's  purpose of taking the Gentiles to be His people under the Messiah, without subjecting them to the Law of Moses.  This is what Paul here calls the preaching of Jesus Christ; for without this he did not think that Christ was preached to the Gentiles as he ought to be; and therefore in several places of his epistle to the Galatians he calls it “the truth,” and the “truth of the Gospel,” and uses the like expressions to the Ephesians and Colossians. 

“and the preaching of Jesus Christ”
Literally:  “And the proclamation of Jesus Christ.”–Not his personal preaching; but according to that preaching of which Christ is the Author and the Subject; and           particularly, as the following clause shows, to the doctrines by which the partition between the Jews and the Gentiles was broken down, and by which they were admitted to the same privileges and hopes.

            PREACHING: (Grk.–kêrugma)–Literally: “proclamation.” It was the proclamation of  Jesus Christ in his Gospel that Paul was referring to.  The words,      “according to the revelation” are recognized  to be  with “preaching.”

“according to the revelation of the mystery”–This is that mystery which he is so much concerned that the Ephesians should understand and adhere to firmly, and which was revealed to him according to that Gospel whereof he was made a minister.

          It is probable that this Grand Mystery of bringing the Gentiles into the Kingdom of God, without passing through the rites of the Mosaic Law, was revealed more particularly to Paul than to any other of the apostles, and that he preached it more pointedly, and certainly with more success.
          According to the communication of that which has been so long concealed, but which is now made manifest. The word “revelation,” refers to the publication of the plan by the Gospel.

          MYSTERY: (Grk.–mustêrion)–The word mystery means, “tthat which is hidden” or “concealed,” and is thus applied to any doctrine which was not before known.

It does not mean necessarily that which is unintelligible;. such in the oracles of the “Mystery Religions,” but that which had not before been revealed. The word here seems to refer to the Principal Doctrines of the Gospel; that is, its main truths, which had been concealed, especially from the entire Gentile world, but which were now made known. The Truths of the Gospel, made known obscurely to the Jews in the O.T. were now, by the command of God, clearly revealed to Gentiles as well as Jews.

            “which was kept secret”–Literally: “Having been kept in silence; were not proclaimed or revealed.”  This purpose of calling the Gentiles, and giving them equal privileges to the Jews, without obliging them to submit to circumcision, etc.

 KEPT SECRET:  (Grk.–sigaô)–Literally: “to keep silence, to old one’s peace.”  As used here it means, “to be kept in silence.”

“since the world began”
Literally: “In times eternal; In times of the ages.”–In all past times. This refers particularly to the Gentiles. The Jews had some obscure intimations of these truths, but they were now made known to all the world. Or, as we should say, “They have been always concealed.”

            SINCE THE WORLD BEGAN:  (Grk.-chronos aiônios)–“through times eternal” or, “along with times eternal”–A.T. Robinson.  This expression is referring to the eternal ages before creation.

“But now is made manifest, and by the Scriptures of the prophets, according to the commandment of the everlasting God, made known to all nations for the obedience of faith.”

“But now is made manifest”
Literally: “But now is made plain.–Is revealed, or made known; that which was so long concealed is now revealed. Paul here is referring to the O.T. Scriptures .

 For Paul, the O.T. was essentially a Christian book.  He contended that his Gospel was witnessed to by the Mosaic Law and the prophets, and in that sense the “mystery” was made known through them.

            MANIFEST:  (Grk.–phaneroô)—“ is revealed, or made known.”  Paul often uses this word.  That which was concealed so long is now divulged; i.e., God's plan of saving men is now made known to all nations.  Revealed now, under the N.T. Dispensation, and by my preaching. \\

“by the scriptures of the prophets”
Literally: “And through prophetic scriptures.”–Not meaning the books of the prophets, but passages referring to this subject contained in their writings.  The apostles constantly made use of them in proclaiming the
Gospel Mystery. 

By the writings of the prophets. The prophetic writings obscurely contained the doctrines, indeed, but so as to be an important means of disseminating and confirming the truth, that the Gentiles should be made acquainted with the Gospel. To those writings Paul had repeatedly appealed in his defense of the proposition, that the gospel was to be preached to the Gentile world, chapters 10, 11, 15. The prophetic writings, moreover were extensively scattered among the Gentile nations, and thus were readily appealed to in defense of this position. Their writings being thus translated, and read, were an important means of propagating the truths of the Christian faith. 

“according to the commandment of the everlasting God”–By His command through Jesus Christ; made known in the Gospel of His Son.  God Who is eternal, and therefore   be revealed. Paul conceives that God is in charge of the redemptive work and gives his      orders (1:1-5; 10:15).

              EVERLASTING:  (Grk.–aiônios)–Literally meaning, “without beginning and     without end; eternal.”  The word, “eternal,” is the better rendering, since something that is everlasting may have a beginning. The same adjective is here applied to God that is used of eternal life and eternal punishment in Matt. 25:46.

“the obedience of faith”|
Literally:  “For obedience of faith.”  In order to lead them to exercise faith in
Christ and be saved.

Lest they should think, from what he had just said, that God had brought in upon His people so vast a change on their condition without giving them any previous notice, Paul here adds that, on the contrary, “the Scriptures of the prophets” contain all that he and other preachers of the Gospel had to declare on these topics, and indeed that the same “everlasting God,” Who  “from eternal ages” had kept these things hid, had given “commandment”  that they should now, according to the tenor of those prophetic Scriptures, to be imparted to every nation for their believing acceptance.

“To God only wise, be glory through Jesus Christ for ever.   Amen.”

“To God only wise”
Literally:  “To {the} only wise God.”–Better: “To God alone wise”–A.T. Robinson.  Paul here resumes his doxology.

        He alone, Who is the Fountain of wisdom and knowledge. He had all this mystery in Himself; and He alone who knew the times, places, persons, and circumstances, could reveal the whole; and He has revealed all in such a way as not only to manifest His unsearchable wisdom, but also His infinite goodness: therefore, to Him be glory for His wisdom in devising this most admirable plan; and His goodness in sending Christ Jesus to execute it; to Him, through Christ Jesus, be glory forever!  Because this plan is to last forever; and is to have no issue but in eternal glory.
           The Author of all true wisdom, especially the display of it made in the Gospel.  As God is the Author of all good, and all our mercies come through Christ, we should be disposed, for all the blessings we receive, especially for the gospel and the hope of heaven, to render to him, through Jesus Christ, glory and honor, thanksgiving and praise for ever. Amen.
            The attribute of wisdom is here brought into view, because it had been particularly displayed in this plan which was now revealed. It evidences, in an eminent degree, the wisdom of God.  That wisdom was shown in devising the Plan of Salvation; in adapting it to the renewing of the heart; the justification of the sinner; his preservation, guidance, and sanctification; and in the manner in which the Divine attributes had all been seen to harmonize. All this Paul had illustrated in the previous parts of the epistle; and now, full of the convictions of this wisdom, he desires that all the praise and honor should be to God. The tendency of the plan is to promote the glory of God.  The obligation on all who are benefited by it is to give Him praise.

            “be glory”– Be praise; honor.

“through Jesus Christ”By means of the work which Jesus Christ has performed; through Him now as Mediator and Intercessor in the heavens (I John 2:1-2).

          The subscription, “written to the Romans from Corinthus, and sent by Phebe servant of the church at Cenchrea” is evidently added by some other hand, but by whom is unknown. Paul assuredly would not write this to inform the Romans that it was sent by Phebe, whom he had just commended to their kindness. It has been known that no reliance is to be placed on any of the subscriptions to the epistles. Some of them are known to be false. By whom they were added is unknown.
            That this epistle was written from Corinth is almost universally believed. It has already been noted that the subscriptions to the sacred books are of little or no authority, all having been added in latter times, and frequently by injudicious hands.  The most ancient have simply To the Romans, or the Epistle to the Romans is finished.  The word Amen was seldom added by the inspired writers, and here it is wanting in almost all the ancient MSS.