12 For we do not commend ourselves again to you, but give you opportunity to boast on our behalf, that you may have an answer for those who boast in appearance and not in heart.
and not in heart [genuineness].
The true basis for determining credibility is the “heart,” not “appearance.” False teachers in Corinth gloried in how they looked to others. This may have involved their eloquence or learning. Their opponents ministered out of appearance rather than from the integrity of motives.
However, Paul’s team’s conscience bore testimony to their integrity here and in 2 Corinthians 1:12. There is a clear connection between how people act and their integrity (“heart”).
At the foundation of doing evangelism is the heart to do it.
How Christians live out the gospel has a significant effect on their ministry (2 Co 3:1-2). God puts little stock in personal credentials (1 Sa 16:7; 2 Co 5:16). It is our heart that matters, as we saw previously in 2 Corinthians 3:3 (not emotions necessarily). Paul was not solely concerned about this reputation; his concern was the reception of the gospel (1 Co 4:1). His concern was eternal values, heaven and hell, winning the lost, and building believers in the faith. Outward religious appearance is a plague in churches today. Appearance is little in comparison to integrity or character.
If there is anything whereby the Christian can boast, it is the Lord Himself (1 Co 1:31; 2 Co 10:17). We cannot take credit for what happens in our ministry. If God did it, He gets the glory.