For this cause... — After much discussion of the construction of this verse, there seems little doubt that the nominative, “I, Paul,” must be carried on beyond the digression upon the mystery of the gospel, and his part in ministering it, which follows. The only question which can well be raised is whether the resumption takes place at Ephesians 3:13, “I desire that ye faint not;” or at Ephesians 3:14, “I bow my knees;” and this seems decided for the latter alternative, both by the emphatic repetition of “for this cause,” and by the far greater weight and finality of the latter sentence.
The prisoner of Jesus Christ. — The phrase (repeated in Ephesians 4:1; Philemon 1:9; 2 Timothy 1:8) is dwelt upon with an emphasis, explained by St. Paul’s conviction that “his bonds” tended to “the furtherance of the gospel” — not merely by exciting a sympathy which might open the heart to his words, but even more (see Philippians 1:13-14) by showing the victorious power of God’s word and grace — which “is not bound” — to triumph over captivity and the danger of death. The expression itself is notable. When St. Paul calls himself the “prisoner of Jesus Christ,” he represents our Lord’s own will, as ordaining his captivity for His own transcendent purposes of good, making him an “ambassador in chains” (Ephesians 6:20), and these “the bonds of the gospel.” (See Philemon 1:13; and Acts 28:20, “For the hope of Israel I am bound in this chain.”) Hence in this passage St. Paul seems to speak of his captivity as a special proof of the reality of his mission, and a new step in its progress; and appeals to it accordingly, just as in the final salutation of the Colossian Epistle, “Remember my bonds.” The whole idea is a striking instance of the spiritual alchemy of faith, turning all things to good — not unlike the magnificent passage (in 2 Corinthians 11:23-30) of his “glorying in his infirmities.”
For you Gentiles. — This was literally true of the origin of his captivity, proceeding as it did from the jealousy of the Jews, excited by the free admission of the Gentiles to the Church; but the reference is not to be limited to this. St. Paul regards the captivity as only one incident in a mission sending him entirely to the Gentiles (Acts 21:21; Romans 11:13; Galatians 2:9). From these words the digression of Ephesians 3:2-13 starts, bringing out the reality and greatness of that mission.