7:1-3 Since God lives in us and we are his children (2 Corinthians 6:16-18), we should now live holy lives out of reverence for Him. Paul’s encouragement to the Corinthians includes an entreaty: we love you, so please listen to us. Don’t shut us out!
7:4-16 And Paul is encouraged that they won’t. There had been an issue in the church (perhaps related to 1 Corinthians 5:1, or something else dealing specifically with an attack on Paul and his apostleship, or both), and Paul wrote a letter that had made them sad. But they listened to what he said! Titus reported back to Paul that they had not only encouraged and refreshed him, but they had responded appropriately to Paul’s letter. They repented of the wrong they were engaging in (in fact, they met Titus with “fear and trembling“) and reaffirmed their concern for Paul. He ends by rejoicing that his confidence in them wasn’t misplaced.
In addition to the reminder to live holy lives, we are also reminded that “sadness as intended by God produces a repentance that leads to salvation, leaving no regret, but worldly sadness brings about death.” Salvation here probably doesn’t mean our initial conversion, but growth and progress in our Christian life. While repentance is necessary for conversion, it is also necessary for Christian maturity. True repentance leads us to a right and growing relationship with God, but simple sadness doesn’t do that. The key here is probably that repentance can mean “a change of mind.” Sorrow doesn’t necessarily mean change, and continuing in our sinful excesses can certainly bring death!