Sanhedrin 5A

ואם היה מומחה לרבים, דן אפילו יחידי. אמר רב נחמן: כגון אנא דן דיני ממונות ביחידי. וכן אמר רבי חייא: כגון אנא דן דיני ממונות ביחידי.

But if one was a judge accepted as an expert for the public, then he may judge cases even as the lone judge. Rav Naḥman said: One such as I may judge cases of monetary law as the lone judge. And similarly, R' Ḥiyya said: One such as I may judge cases of monetary law as the lone judge.

איבעיא להו: כגון אנא דגמירנא וסבירנא ונקיטנא רשותא, אבל לא נקיט רשותא ⁠– דיניה לא דינא? או דילמא: אף על גב דלא נקיט רשותא ⁠– דיניה דינא?

A dilemma was raised before the rabbis: What is the meaning of: Such as I, in the statements of these Rabbis? Did they intend to say: Such as I, in that I have studied and have the skills to extrapolate and derive new rulings on the basis of earlier decisions, and have also received permission to judge as the lone judge? But accordingly, if one has not received permission to judge as the lone judge, his judgment is not a valid judgment? Or perhaps this is not the correct reading of the statements, and the halakha is that even though he did not receive permission to judge as the lone judge, his judgment is nevertheless a valid judgment?

תא שמע: דמר זוטרא בריה דרב נחמן דן דינא וטעה, אתא לקמיה דרב יוסף. אמר לו: אם קיבלוך עלייהו ⁠– לא תשלם, ואי לא ⁠– זיל שלים. שמע מינה: כי לא נקיט רשותא ⁠– דיניה דינא. שמע מינה.

The Talmud suggests: Come and hear a solution to this dilemma from the following case: Mar Zutra, son of Rav Naḥman, once adjudicated a certain case and erred in his ruling. Upon recognizing his error, he came before Rav Yosef to ask what he should do. Rav Yosef said to him: If the litigants accepted you upon themselves as the lone judge, and both had agreed that they would accept your ruling, you are not liable to pay restitution to the party who lost the case due to your erroneous ruling. But if they did not accept you on themselves, but were rather compelled to be judged before you, you must go and pay restitution. And learn from it that even in a case where one did not receive permission to judge as the lone judge, his ruling is a valid judgment. The Talmud affirms: Learn from it that this is the case.