Yehudah Ben Tabbai And Shimon Ben Shatach Received [The Oral Tradition] From Them. Yehudah Ben Tabbai Said: "Do Not Act As A Counselor [When Sitting As A Judge]. When The Litigants Stand Before You, Regard Them Both As Guilty, But When They Leave, Having Accepted The Judgment, Regard Them Both As Guiltless."
Reshoim, translated as "guilty," also means "wicked." The very fact that two people are involved in a dispute severe enough to bring them before a judge appears to indicate that both possess a certain measure of wickedness. When two people cannot resolve their differences without arbitration, both need to increase their love for their fellow man.
(Likkutei Sichos, Vol. XXIV, p. 155)