John Chrysostom

Then he makes him respected also from the judgment of those that had chosen him. And this too is no light matter. Therefore after saying, "Whose praise in the Gospel is spread through all the churches," he added, "And not only so." What is, "and not only so?" 'Not only on this account,' he says, 'is respect due to him, that he is approved as a preacher and is praised by all.' "But he was also appointed by the churches along with us." Whence it seems to me, that Barnabas is the person intimated. …

Homily 18 on 2 Corinthians ↗

Theophylact of Ohrid

He praises the man also by the judgment of those who chose him: not only, he says, is he renowned as one who worthily preaches the Gospel, but he has also been chosen by the churches to accompany us, so that he might be a partaker with us both in trials and in dangers. This is more fitting for Barnabas. "Chosen" for this grace, that is, for the administration of the offerings, so that he might serve with us. …

Commentary on 2 Corinthians ↗