Gemara Megillah 7b:
??? ??? ?????? ????? ?????? ?????? ?? ??? ??? ??? ???? ??? ????? ?????
??? ???? ???? ???? ????? ????? ???? ????
?????? ?? ??? ????? ???? ???? ???? ??? ???? ??????
“Rava said: A person is obligated to become intoxicated on Purim until he does not know the difference between ‘Cursed Be Haman’ and ‘Blessed Be Mordechai.’
Rabba and Rabbi Zera made their Purim feast with one another. They became drunk; Rabba arose and slaughtered Rabbi Zera. The next day, he asked for mercy for him, and caused him to live.”
The Rif, Rosh, and Tur simply cite the Gemarah from Rava lehalacha, without elaboration.
Shulchan Aruch:
???? ???? ?????? ?????? ?? ??? ??? ??? ???? ??? ????? ?????
Shulchan Aruch [Directly quoting the gemara]: One is obligated to [get drunk]
Rambam:
???? ??
???? ???? ????? ?? ????? ??? ????? ????? ??? ??? ??? ???? ???, ????? ??? ?? ?????? ????? ??????.
Chazal:
Wine has potential for good and bad. Chazal mention this idea in many places. Getting drunk, if done properly, is an important mitzvah.
For 364 days a year, we have no other choice. Our mind must exercise complete control over our emotions and behavior, lest the animal in us rage rampant and trample to death all that is good in ourselves and our world. Furthermore, we need the mind not only as guardian and regulator, but also as facilitator of our highest potentials. It is the mind that navigates the workings of nature, enabling us to sustain and improve our lives in the service of our Creator; it is the mind that recognizes the goodness and desirability in certain things and the evil and danger in others, thereby guiding, developing and deepening our loves and aversions, our joys and fears; it is with our minds that we imbibe the wisdom of the Torah, allowing us an apprehension of the divine truth.
If the mind does all these things within the finite parameters of reason, concealing galaxies of knowledge with every ray of light it reveals and suppressing oceans of feeling with every drop it distills, it remains the most effective tool we have with which to access the truths that lie buried in the core of our souls and reside in the subliminal heavens above.
But there is one day in the year in which we enjoy direct, immediate access to these truths. This day is Purim. The Jew who rejoices on Purim–who rejoices in his bond with G-d without equivocation–has no need for reason. For he is in touch with his truest self–a self before which his animalistic drives are neutralized, a self which requires no medium by which to express itself and no intermediaries by which to relate to its source in G-d.
The Jew who rejoices on Purim no longer requires the mind to tell him the difference between “cursed be Haman” and “blessed be Mordechai”; he is above it all, relating to the divine truth that transcends the bifurcation of good and evil. For the Jew who rejoices on Purim, the mind is utterly superfluous, something which only encumbers the outpouring of his soul, something which only quantifies and qualifies that which is infinite and all-pervading. So he puts his mind to sleep for a few hours, in order to allow his true self to emerge.