הלכה על מגילה 1:8

The Gemara records the incident involving Rabbah and Rabi Zeira to reject or limit the rabbinical decree regarding drinking on Purim. The Baal Hamaor (Megillah 3b in the Rif's pages) cites and accepts the opinion of Rabbeinu Ephraim that the Gemara presents the incident to rescind this Halachah, and to conclude that it is now improper to drink on Purim. On the other hand, the Rif (ibid.) and the Rosh (Megillah 1:8) cite the obligation to drink on Purim without any reservations whatsoever. Although they reject the approach of Rabbeinu Ephraim, they presumably believe that the Gemara presents the story as a cautionary note. Thus, although the Shulchan Aruch (ad. loc.) rules in accordance with the Rif and Rosh, the Rabbah and Rabi Zeira incident sounds a cautionary note to ensure that observance of this Halachah does not lead to serious problems.

The Gemara might record the incident involving Rabbah and Rabi Zeira to reject or limit the rabbinical decree regarding drinking on Purim. The Baal Hamaor (Megillah 3b in Rif's pages) cites and accepts the opinion of Rabbeinu Ephraim that the Gemara presents the incident to rescind this Halachah, so it is now improper to drink on Purim. On the other hand, the Rif (ibid.) and the Rosh (Megillah 1:8) cite the obligation to drink on Purim without any reservations whatsoever. Apparently, they believe that the Gemara presents the story merely as a cautionary note, with no impact on the Halachah.