Jamieson, Fausset and Brown on 1 Corinthians 4:3

3. it is a very small thing--literally, "it amounts to a very small matter"; not that I despise your judgment, but as compared with God's, it almost comes to nothing.

judged ... of man's judgment--literally, "man's day," contrasted with the day (1Co 3:13) of the Lord (1Co 4:5; 1Th 5:4). "The day of man" is here put before us as a person [Wahl]. All days previous to the day of the Lord are man's days. Emesti translates the thrice recurring Greek for "judged ... judge ... judgeth" (1Co 4:4), thus: To me for my part (though capable of being found faithful) it is a very small matter that I should be approved of by man's judgment; yea, I do not even assume the right of judgment and approving myself--but He that has the right, and is able to judge on my case (the Dijudicator), is the Lord.