Commentaries:
Robertson's Word Pictures (NT)
We are bound (ofeilomen). Paul feels a sense of obligation to keep on giving thanks to God (euxaristein tw qew, present infinitive with dative case) because of God's continued blessings on the Thessalonians. He uses the same idiom again in II Thessalonians 2:13 and nowhere else in his thanksgivings. It is not necessity (dei) that Paul here notes, but a sense of personal obligation as in I John 2:6 (Milligan).
Even as it is meet (kaqwv acion estin). Ofeilomen points to the divine, acion to the human side of the obligation (Lightfoot), perhaps to cheer the fainthearted in a possible letter to him in reply to Paul's First Thessalonian epistle (Milligan). This adjective aciov is from agw, to drag down the scales, and so weighty, worthy, worthwhile, old word and appropriate here.
For that your faith groweth exceedingly (oti uperaucanei h pistiv umwn). Causal use of oti referring to the obligation stated in ofeilomen. The verb uperaucanw is one of Paul's frequent compounds in uper (uper-bainw, I Thessalonians 4:6; uper-ek-teinw, II Corinthians 10:14; uper-en-tugxanw, Romans 8:26; uper-nikaw, Romans 8:37; uper-pleonazw, I Timothy 1:14) and occurs only here in N.T. and rare elsewhere (Galen, Dio Cass.). Figure of the tree of faith growing above (uper) measure. Cf. parable of Jesus about faith-like a grain of mustard seed (Matthew 13:31 f.).
Aboundeth (pleonazei). Same verb in I Thessalonians 3:12, here a fulfilment of the prayer made there. Milligan finds diffusive growth of love in this word because of "each one" (enov ekastou). Frame finds in this fulfilment of the prayer of I Thessalonians 3:12 one proof that II Thessalonians is later than I Thessalonians.
Other Robertson's Word Pictures (NT) entries containing 2 Thessalonians 1:3:
Romans 5:20
1 Thessalonians 1:2
2 Thessalonians 1:11
2 Thessalonians 2:13
2 Timothy 1:3
2 Peter 1:5
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