Eruvin 32A

בשל סופרים ⁠— חזקה שליח עושה שליחותו. ורב ששת אמר: אחד זה ואחד זה ⁠— חזקה שליח עושה שליחותו.

However, with regard to rabbinic laws, we do rely on the presumption that an agent fulfills his agency. And Rav Sheshet disagreed and said: With regard to both this, Torah law, and that, rabbinic law, we rely on the presumption that an agent fulfills his agency.

אמר רב ששת: מנא אמינא לה, דתנן: משקרב העומר, הותר החדש מיד.

Rav Sheshet said: From where do I say this? As we learned in a Mishnah: Once the omer has been offered, the grain from the new crop is immediately permitted. The Torah prohibits eating from the new crop of grain until the omer sacrifice is offered on the 2nd day of Passover (Leviticus 23:14); once the omer is offered, it is immediately permitted to partake of the new grain.

והרחוקים מותרים מחצות היום ואילך. והא חדש דאורייתא הוא, וקתני: הרחוקים מותרין מחצות היום ואילך. לאו משום חזקה שליח עושה שליחותו?

And those far from Jerusalem, who do not know whether or not the omer has already been offered, are permitted to eat from the new crop from midday and on, as the omer must surely have been offered by this time. Isn’t the prohibition to eat from the new crop a Torah law? And nevertheless, it was taught: And those far from Jerusalem are permitted to eat from the new crop from midday and on. Is this not because we may rely on the presumption that an agent fulfills his agency? The priests in the Temple serve as the agents of the entire Jewish people, and it may be assumed that they have performed the mission entrusted to them.

ורב נחמן? התם כדקתני טעמא ⁠— לפי שיודעין שאין בית דין מתעצלין בו.

The Talmud asks: And how does Rav Naḥman, who holds that with respect to Torah laws we may not rely on the presumption that an agent fulfills his agency, refute this proof? He can respond as follows: There, the agents may be trusted for the reason that was explicitly taught: Because we know that the court will not be indolent in offering the omer sacrifice; however, the same cannot be said of ordinary agents.