1 Corinthians 4:3 - Matthew Poole's English Annotations on the Holy Bible

Those who said, I am of Apollos, and I am of Cephas, did at least tacitly judge Paul, and prefer Apollos and Cephas before him; and it is probable, and will appear also from other parts of these Epistles, that they passed very indecent censures concerning Paul: he therefore tells them, that he valued very little what they or any other men said of him. In the Greek it is, of man's day; but it is generally thought that our translators have given us the true sense, in translating it man's judgment, day being put for judgment; as Jeremiah 17:16, where woeful day signifies woeful judgment. So the day of the Lord in Scripture often signifieth the Lord's judgment: the reason of that form of speech seems to be, because persons cited to a court of judgment use to be cited to appear on a certain day. Yea, I judge not mine own self; yea, saith the apostle, I pronounce no sentence for myself, I leave myself to the judgment of God. I may be deceived in my judgment concerning myself, and therefore I will affirm nothing as to myself.