Eruvin 41B

דאי סלקא דעתך אכולהו ⁠— הא בעי מיניה רבה מרב יהודה ולא פשט ליה!

as, if it should enter your mind to say that Rav Yehuda said that the halakha is in accordance with the opinion of the Rabbis with regard to all the cases in the Mishnah, including that of the 9th of Av that occurs on Friday, there is a difficulty: Didn’t Rabba raise a dilemma before Rav Yehuda with regard to this issue, and he did not answer him? This demonstrates that he did not have a decisive ruling on this subject.

ולטעמיך, הא דדרש מר זוטרא משמיה דרב הונא: הלכה, מתענה ומשלים. הא בעא מיניה רבה מרב הונא ולא פשט ליה?!

The Talmud responds: And according to your opinion, that the issue had not been resolved, there is a difficulty with that which Mar Zutra expounded in the name of Rav Huna: The halakha is that one fasts and completes the fast on Friday. Didn’t Rabba also raise this dilemma before Rav Huna, and he too did not answer him? How could Mar Zutra have reported this halakhic ruling in the name of Rav Huna?

אלא: הא ⁠— מקמי דשמעה, והא ⁠— לבתר דשמעה, הכא נמי: הא ⁠— מקמי דשמעה, הא ⁠— לבתר דשמעה.

Rather, you must say that this dilemma that Rabba raised to Rav Huna was before Rav Huna heard Rav’s ruling on the subject; whereas this, i.e., Rav Huna’s statement as cited by Mar Zutra, was made after he heard Rav’s ruling on the matter, and the problem was resolved for him. Here, too, with regard to Rav Yehuda, we can say that this dilemma that Rabba raised before Rav Yehuda was before Rav Yehuda heard Rav’s ruling on the topic, and therefore he did not know how to answer Rabba; whereas this, i.e., Rav Yehuda’s statement in the name of Rav, was made after he heard it.