John Gill Commentary 1 Corinthians 3:4

"For when one saith, I am of Paul; and another, I am of Apollos; are ye not men?" — 1 Corinthians 3:4 (ASV)

For while one says, I am of Paul
This shows what their envying and strife, and divisions were about, and from where they sprung; and which serve, to strengthen the proof, and support the charge of carnality brought against them; for when one sort made a party for Paul, and set up him as their minister above all others; and said

another, I am of Apollos ,
preferring him for his eloquence above Paul, or any other preacher, as appears from (1 Corinthians 1:12) there was a third sort for Cephas, whom they cried up as superior to the other two, or any other man; and a fourth were for Christ, and despised all ministers whatever:

are you not carnal ?
all this was a demonstration of it: they could never clear themselves from it, they must be convicted in their own consciences of it; to which the apostle appeals: the Alexandrian copy and the Vulgate Latin and Ethiopic versions read, "are you not men?"