Why is it wrong to give others the impression that you are more spiritually blessed than they are?
It is wrong because it breeds carnal pride and division, puffing believers up against one another and exalting human leaders above what is written. Paul insists no one should be puffed up for one against another, since no person makes himself to differ spiritually.
Les explains that the Corinthian congregation had become puffed up, each claiming importance because he followed Peter, Paul, or Apollos. Paul used himself and Apollos as a figure so they would learn not to think of men above what is written. Such boasting was infantile and carnal. The practical lesson is that no one may give others the impression of being better or more spiritually blessed, because verse 7 asks, “whom maketh thee to differ?” and forbids being puffed up for one against another.
And these things, brethren, I have in a figure transferred to myself and to Apollos for your sakes; that ye might learn in us not to think of men above that which is written, that no one of you be puffed up for one against another.