A.T. Robertson Commentary 2 Corinthians 12:9

"And he hath said unto me, My grace is sufficient for thee: for [my] power is made perfect in weakness. Most gladly therefore will I rather glory in my weaknesses, that the power of Christ may rest upon me." — 2 Corinthians 12:9 (ASV)

He hath said (ειρηκεν). Perfect active indicative, as if a final word. Paul probably still has the thorn in his flesh and needs this word of Christ.

Is sufficient (αρκε). Old word of rich meaning, perhaps kin to Latin arceo, to ward off against danger. Christ's grace suffices and abides.

Is perfected (τελειτα). Present passive indicative of τελεω, to finish. It is linear in idea. Power is continually increased as the weakness grows. See Php 4:13 for this same noble conception. The human weakness opens the way for more of Christ's power and grace.

Most gladly rather (ηδιστα μαλλον). Two adverbs, one superlative (ηδιστα), one comparative (μαλλον). "Rather" than ask any more (thrice already) for the removal of the thorn or splinter "most gladly will I glory in my weaknesses." Slowly Paul had learned this supreme lesson, but it will never leave him (Romans 5:2; 2 Timothy 4:6–8).

May rest upon me (επισκηνωση επ' εμε). Late and rare verb in first aorist active subjunctive with ινα (final clause), to fix a tent upon, here upon Paul himself by a bold metaphor, as if the Shechinah of the Lord was overshadowing him (cf. Luke 9:34), the power (δυναμις) of the Lord Jesus.