Struggle (1-2): Paul elaborates[1] on the arduous effort ("struggle")[2] that he puts out for God's people, even for those he's never met.[3] He ministers to them through his prayers (1:9ff) and his concern (2 Cor. 11:28-29) and his letters.[4] More than that, he suffers for their sake (1:24). Paul sets aside personal ease and willingly endures conflicts and persecutions for the Gentile churches.[5] He would rather suffer than to betray them by compromising the gospel Christ meant for the nations (Gal. 1:6-12; 2:1-5). He thus labors to[6] encourage the churches toward a unity in love and a deep conviction in their faith in Christ.[7]
Stability in Christ (3-5): Knowing Christ is the pivotal need of the church, for in Christ we have "all the treasures of wisdom and knowledge." To be guarded from deluding influences and persuasive arguments that can lead us astray (2:4), we must know Christ truly. And it goes without saying that we know Christ by knowing His words![8] This continues to be Paul's aim in his labors: to make Christ known. Even in his absence, he still wishes to minister to them in this way (even from prison!). He does this joyfully, and He anticipates that they will exhibit spiritual maturity marked by discipline and stability.[9]
[1] Paul begins this section with the conjunction "For [gar (γάρ)]," giving a further explanation of the foregoing.
[2] "Struggle" is a cognate of "strive" (1:29), both depicting an athlete's exertion of effort (cf. 1 Cor. 9:25).
[3] Paul suffered for those he did not meet (2:1)—the emphasis here—and those he did meet (cf. Phil. 2:17).
[4] This epistle is an example, as also Ephesians and Philippians. He proclaims Christ with the pen (1:28-29).
[5] He suffers as a prisoner "for the sake of you Gentiles" (Eph. 3:1). Cf. also Acts 21:27-29; 22:21-24.
[6] 2:2 points out the purpose for which Paul struggled ("that" is literally "in order that [hi-na (ἵνα)]").
[7] NASB's "attaining to…" and "resulting in…" are parallel purpose phrases, literally, "for [eis (εἰς)]…" This means that "all the wealth..." and "true knowledge" are both pointing to a deep conviction in Christ.
[8] Knowing Christ goes hand in hand with knowing His word. Paul points this out in 3:16. Cf. also 1 John 2:3-6.
[9] Paul hopes to see "your good discipline and the stability of your faith in Christ." What he means here is best understood in light of how he practically works out the high view of Christ (1:15-20) in the rest of this letter.