Related for Eruvin 74:9
א"ל רבא לרב נחמן מאן האי תנא דאפילו בדרבנן לית ליה ברירה דתניא אמר לחמשה הריני מערב על איזה מכם שארצה רציתי ילך לא רציתי לא ילך רצה מבעו"י עירובו עירוב משחשיכה אין עירובו עירוב
while it was yet day,<span class="x" onmousemove="('comment',' Of the Sabbath eve.');"><sup>26</sup></span> [but if he did it] after dusk the 'erub is not effective'?<span class="x" onmousemove="('comment',' Since at twilight, when the validity of an 'erub must be determined, he may have intended his 'erub for a different person and his subsequent selection cannot be made retrospective. Now, since 'erub is a Rabbinical enactment, it follows that bererah is inapplicable even to Rabbinical enactments, and the question is who is that Tanna?');"><sup>27</sup></span> The other remained silent and gave him no answer whatever. But why could he not tell him that the Tanna was one of the school of Ayo?<span class="x" onmousemove="('comment',' Who ruled (supra 36b) that, according to R. Judah, bererah is not applied to 'erub though it is only a Rabbinical enactment.');"><sup>28</sup></span>