The clause reading τοῖς ἀγαπῶσι τὸν θεὸν πάντα συνεργεῖ εἰς ἀγαθόν can be translated in two major ways (see the “Notes on the Text and Translation” concerning the presence or absence of ό θεός), depending on how one construes the syntax and makes a choice concerning the subject. Grammatically it is possible that the subject is πάντα, taking it to be the neuter nominative plural of πάν. That is possible, because a neuter nominative plural noun takes a third person singular verb (which συνεργεί [“works together”] is). On the other hand, it is possible that πάντα is a neuter accusative plural. In that case, it could be an accusative of respect, and the subject of the clause would then be “he” (meaning “God”). Modern translations go in both directions. Those in the former group include:
KJV: “And we know that all things work together for good to them that love God.”
ASV: “And we know that to them that love God all things work together for good.”
NAB: “We know that all things work for good for those who love God.”
NRSV: “We know that all things work together for good for those who love God.”
NET: “And we know that all things work together for good for those who love God.”
ESV: “And we know that for those who love God all things work together for good.”
Those in the latter group (some of which insert “God” for clarification) include:
RSV: “We know that in everything God works for good with those who love him.”
NEB: “And in everything, as we know, he cooperates for good with those who love God.”
NIV: “And we know that in all things God works for the good of those who love him.”
NASV: “And we know that God causes all things to work together for good to those who love God.”
The latter course is to be preferred. The primary reason for that is that “he” (= “God”) is the subject of verses both prior to and after this one (8:27; 8:29-30). One can expect that “he” would be the subject of this clause as well. Those ancient scribes who added ό θεός as the subject must have sought to clarify the sentence, which the translators of the RSV and NIV did as well, making similar judgments. And even though it has been said that the difference in meaning is not great, since either reading expresses confidence in the sovereignty of God, there is actually a profound difference. In the first instance, Paul is saying that everything works out well for those who love God. This has the ring of the optimism of modern times, although it need not, for it could mean that all that one endures (even suffering) works together for a good outcome, which could include final salvation. Still, in the final analysis, the “all” then appears to transpire for good with or without God’s involvement. In the second instance, however, Paul is saying that God works for the good of all who love him in every conceivable situation. Whatever one faces (including suffering), God is present and active to work for a good outcome, which may well be realized only eschatologically in final salvation, but ultimately the promise is sure. That perspective coheres theologically with the rest of this section (8:18-30), which sees suffering — both on the part of humans and of the rest of creation — in light of eschatological hope.
Arland J. Hultgren, Paul’s Letter to the Romans, A Commentary.