Paul, a servant of Jesus Christ, called to be an apostle. In his salutations to the Philippians and to Titus also St. Paul calls himself δοῦλος (i.e. "bondservant") of Jesus Christ; but usually only ἀπόστολος, or, as here, κλητὸς ἀπόστολος, which is rightly translated in the Authorized Version, "called to be an apostle," Divine vocation to the office being the prominent idea.
St. Paul often elsewhere insists on the reality of his vocation from Christ himself to be an apostle to the Gentiles; and this with regard to disparagement of his claim to be a true apostle at all on the part of some (cf.
1 Corinthians 9:1; 2 Corinthians 11:5; 2 Corinthians 12:12; Galatians 1:1, Galatians 1:12; Galatians 2:8). It does not follow from his thus asserting his claim here and afterwards in this Epistle that he was aware of any disparagement of it at that time among the Roman Christians; still less that he wrote his Epistle with a polemical purpose against the Judaizers, as some have supposed.
Still, he may have suspected that some might possibly have been busy there, as they were in other places; and, however that might be, writing as he was to a Church not founded by, and as yet unvisited by, himself, he might think distinct assertions of his claim to be heard desirable.
Separated (or, set apart) unto the gospel of God; i.e. to the preaching of the gospel, not the reception of it only, as is evident from the context. The word ἀφωρίσμενος here, as well as the previous κλητὸς, is best taken, in pursuance of the line of thought, as referring to the Divine counsels, not to the agency of the Church.
It is true that the word is elsewhere used with the latter reference, as in Acts 13:2, ἀφορίσατε δὴ μοι τόν τε βαρνάβαν καὶ τὸν, σαῦλον εἰς τὸ ἔργον ὂ ππροσκέκλημαι αὐτούς, where the ἀφορισμὸς spoken of was subsequent to the Divine κλῆσις, and effected by human laying on of hands.
But we have also St. Paul's own words (Galatians 1:15), ὁ θεὸς ὁ ἀφόρρισας με ἐκ κοιλίας μητρός μου καὶ καλίσας διὰ τῆς χάριτος αὐτοῦ, where the ἀφορισμὸς is that of God's eternal purpose, and previous to the κλῆσις (cf.
Acts 9:15 and Acts 26:16, Acts 26:17).