In addition to the four Mitzvot of Purim, there is an additional Halacha that one should drink on Purim, until he cannot differentiate between the phrases, “Arur Haman” and “Baruch Mordechai” (Megilla 7b). The Gemara states in accordance with Rava that there is, in fact, a Mitzvah to drink on Purim. This opinion, in the Gemara, is followed by an ambiguous story. This story can either be understood as a support to this opinion, or as a refutation. In this story Rabba and Rabbi Zaira were eating together for the Purim Seudah, and Rabba killed Rabbi Zaira in a drunken rage. The following morning Rabbi Zaira was reincarnated after Rabba prayed on his behalf. The next year, Rabbi Zaira was invited to eat his Seudat Purim with Rabba, but Rabbi Zaira suggested that they dine separately because he feared Rabba might kill him again, and a miracle is not likely to be repeated. In interpretation of this Gemara, many Rishonim having differing opinions as to the classification of the Mitzvah of drinking on Purim.
The Rif, a Sephardic Rishon, in interpreting the Gemara on 6b omits the story of Rabba and Rabbi Zayra. The apparent reason why the Rif leaves out this story is that he believes that there is a Mitzvah to drink on Purim. The Rav interprets the Rif’s opinion in two ways. One way is that the story of Rabba and Rabbi Zaira happened prior to the ruling of Rava, and therefore if Rava nonetheless ruled that there is a Mitzvah, then there is obviously a Mitzvah to drink.
The Meiri, another Rishon, has a differing opinion as to the Mitzvah of drinking. He believes that we should be Mesameach through other means, and should not get drunk on Purim. The reason he holds like this is that drinking is a frivolous form of Simcha, and that is not how one should celebrate Purim. The story of Rabba and Rabbi Zaira appears to support this view.
A third Rishon, the Avudraham, presents a seemingly ambiguous classification of the Mitzvah. He states that in places where drinking is not common, it is permitted to get drunk on Purim as they have very low tolerance, and do not need to consume much wine in order to get drunk. In places were drinking is very common, such as the country in which the Avudraham lived, it is not permissible for one to get drunk, as one would have to consume a disgusting amount of wine to get drunk.
Although there is a Halacha of drinking on Purim, it is often misunderstood and abused. The first aspect of this Halacha which must be understood is that there is no Mitzvah to drink liquor, as this Halacha only applies to wine as implied by Rashi and the Rambam. Another misconception often incorporated with this Halacha is that drinking does not apply to the nighttime, but rather only during the Purim Seudah. The Mitzvah of drinking is trivial in comparison to other Mitzvot of the day such as Davening, Tefillin, Megillah, etc. and should not compromise the fulfillment of these Mitzvot. It is suggested by the Rama that if one does drink, they should drink only a little more than that which they drink for kiddush on Shabbat, and should than go to sleep, thereby fulfilling the Mitzvah and not compromise one’s safety.
-Adapted from Shiur given by Rabbi Ezra Wiener in TABC.