2 Corinthians 10:12
“For we are not bold to number, or compare in ourselves with some that commend themselves.”
Here he both shows that those false Apostles are boasters and say great things of themselves: and ridicules them as commending themselves. 'But we do no such thing: but even if we shall do any thing great, we refer all unto God, and compare ourselves with one another.' Wherefore also he added,
“But they themselves measuring themselves by themselves and comparing themselves among themselves are without understanding.” Now what he says is this: 'we do not compare ourselves with them, but with one another.' For further on he says, “in nothing am I behind the very chiefest Apostles;” and in the former Epistle, “I labored more abundantly than they all;” and again, “Truly the signs of an Apostle were wrought among you in all patience.” 'So that we compare ourselves with ourselves, not with those that have nothing: for such arrogance comes of folly.' Either then he says this with reference to himself, or with reference to them, that 'we dare not compare ourselves with those who contend with one another and boast great things and do not understand:' that is, do not perceive how ridiculous they are in being thus arrogant, and in exalting themselves among one another.
Source: Homilies on Second Corinthians (New Advent)