The passage
      v25. Paul gives glory to the God who is well able to "establish", to confirm, the Romans in their commitment to the gospel. That is, confirm in the sense of strengthen their commitment to, their belief in, the gospel. The NIV has "establish you by my gospel", but "by" or "through", is probably better translated "according to", "in alignment with". So, Paul gives glory to the God who is well able to keep the Romans in line with gospel truth.
      When Paul uses the phrase, "my gospel", he probably means something like "my message", the content of which is the important message concerning the life and teachings of Jesus Christ. Then he adds, "and the proclamation of Jesus Christ, according to the revelation of the mystery". The "and" is better translated "which is." What Paul is doing is explaining something about the content of his message - ie. the gospel. Of the content he says:
        i] It is the "proclamation of Jesus Christ" - who Jesus is and what he has done. This gospel, focused on the life and teachings of Jesus, is preached, proclaimed, by the apostles.
        ii] It is God's revelation.
        iii] It is a mystery. It is a truth hidden, but now revealed.
      v26. The mystery, now made known in the gospel, is confirmed by the Old Testament scriptures - "made known through the prophetic writings." The gospel represents the fulfillment of the promises detailed in the Old Testament - "The time is fulfilled". Therefore, the Old Testament scriptures confirm and point to the gospel message. This initial revelation, which contained the hidden mystery now revealed in the gospel, was "by the command of the eternal God."
      The revelation of the mystery in the gospel serves to bring about faith among all the Gentiles - so that all nations might discover the obedience that comes from faith. God's purpose is to gather a perfected people to himself out of all the world. He made known this intention to Abraham and he fulfilled it in Christ.
      v27. Finally, Paul gives an ascription of praise to God. The Greek implies that the ascription is to Jesus, but it is likely that God is intended. Paul gives praise to God, the wise one, and he does this through Jesus.

Living the gospel
      Thinking Christianly is something God is ready, willing and able to help us with. To this God, Paul gives praise.
      It's probably true that we don't think "Christianly". Most people these days are no longer objective thinkers. We no longer think in terms of an objective truth that lies beyond ourselves - a truth we have to search out, recognize and submit to. For most modern people, particularly those under 30, truth is subjective; truth is something that is within.
      Yet, the Bible is anything but subjective for it speaks of an objective truth revealed to us by God. This truth is not a matter of opinion, something we can feel about - "I feel it's right", "I feel it's wrong." Divine truth is unchanging and eternal. At the center of this revealed truth is gospel truth, and it is here that we must focus. Our understanding of ourselves and the world must focus on the gospel rather than subjective opinions.
      In our passage for study, Paul the apostle gives us an insight into this gospel, and he reminds us that God is able to align our thinking and behavior to it:
        i] It is the "proclamation of Jesus Christ." The message concerns the person and work of Jesus. The gospel reveals that the Christian walk is all about following in the footsteps of Christ.
        ii] It is God's revelation.
        iii] It is a mystery. The secret was in the Old Testament, hidden in the law and the prophets. The mystery remained hidden for Israel and the world until the coming of Christ.
        iv] The mystery is now revealed in the gospel. The wonderful thing about this mystery is that it is a secret thing now revealed, a riddle for which we know the answer.
        v] The gospel is confirmed by the Old Testament scriptures - "made known through the prophetic writings." With the key of the New Testament we can now see the mystery hidden in the Old Testament.
        vi] Its proclamation is commanded by God. He willed it made known.
        vii] It serves to bring about the righteousness which comes through faith among all the Gentiles. God's intention to gather a perfected people to himself is realized through the gospel.
      Let us be men and women of gospel truth.

v25
      tw/ dunamenw/ (dunamai) pres. pas. part. "to him who is able" - to the one being able. Participle as a substantive. Having the power to make something possible, cf. Eph.3:20, Jd.24. "To him whose power can establish you firmly", Bruce.
      sthrixai (sthrissw) inf. "to establish" - to make firm, make stable, set up, fix firmly. The infinitive is complementary, completing the sense of the verbal aspect of the substantive participle, "is able." The gospel can strengthen the believer, cf. 1:11. "To him who can strengthen you by my gospel", Moffatt.
      kata to euaggelion "by [my] gospel" - according to the message. "According to" is better than "by means of" or "through". "My" means the gospel which Paul preaches which he received from Christ. The phrase is better translated "who is able to confirm you in accord with my gospel", Cranfield.
      khrugma (a) "proclamation" - The apostolic preaching of the cross and resurrection of Christ. The phrase serves to explain Paul's gospel.
      Ihsou Cristou gen. "of Jesus Christ" - Best taken as an objective genitive, "the preaching about Jesus Christ", Morris.
      apokaluyin (iV ewV) "revelation" - unveiling. "The full unveiling of the mystery", Bruce.
      sisighmenou (sigaw) perf. pas. part. "hidden" - having been kept secret, silent, hidden. The participle probably functions here as an adjective, modifying "gospel / mystery". The gospel unveils the mystery, once hidden, but now revealed. "That purpose which for long ages was veiled in silence", Barclay.

v26
      de "but" - Adversative, contrasting the unveiled now with the veiled past.
      nun "now" - The "now" should by underline, "now, however", TEV.
      fanerwqentoV (fanerow) aor. pas. "revealed" - made manifest. It should not be read that the mystery is revealed through the prophets and law (obviously the Old Testament), but that it is revealed through the proclamation of the gospel which is confirmed by the law and the prophets.
      epitaghn (h) "the command" - a command, order, instruction, decree..
      tou aiwniou geou "of the eternal God" - The sense of "eternal" is probably "ever-living", "the One who never dies", but also carrying the sense of "unchanging", "the never-changing One."
      eiV "so that" - into, to, for. Although not a common sense, the preposition here probably expresses purpose, "in order that", as NIV.
      uJpakohn (h) pistewV (iV ewV) - "[that the nations might] believe and obey" - The obedience of faith, cf 1:15. The mystery is revealed in the gospel so that the nations may come to the "obedience of faith", ie. that right-standing before God which is by faith from first to last.