Pirkei Avot §avot_01_08: Judah ben Tabbai and Shimon ben Shetach received [the oral tradition] from them.

Judah ben Tabbai and Shimon ben Shetach received [the oral tradition] from them. Judah ben Tabbai said: do not [as a judge] play the part of an advocate; and when the litigants are standing before you, look upon them as if they were [both] guilty; and when they leave your presence, look upon them as if they were [both] innocent, when they have accepted the judgement.