Megilla 7b
A man is obligated to "mellow oneself" until he does not know the difference between 'cursed is Haman' and 'Blessed is Mordechai.' Raba and Rabbi Zeira made a Purim meal together. They became drunk and Raba arose and slaughtered Rabbi Zeira. The next day he prayed for [divine] mercy and he returned to life. The next year, [Raba] said to [Rabbi Zeira] "Come and let us make a Purim meal together!"[Rabbi Zeira] replied, "Not every single time does a miracle occur."
Maharsha (R. Shmuel Eidels, 1555–1631), in his commentary to this passage, explains that Rabba certainly didn't kill R. Zeira. Rather, he forced him to drink excessively, which made him ill. The Maharsha suggests that the unusual term “shachtei” ("slaughtered") employed by the Gemara refers to what Rabba did to Rabbi Zeira’s throat – forcing him to drink.
What is the connection between the two statements of the Talmud?
It happened in the days of Ahasuerus…
In those days, when King Ahasuerus occupied the royal throne in the fortress Shushan, in the third year of his reign, he gave a banquet for all the officials and courtiers…the nobles and the governors of the provinces in his service. For seven days…royal wine was served in abundance, as befits a king, in golden goblets of varied design. And the rule for the drinking was, “No restrictions!” For the king had given orders to every palace steward to comply with each man’s wishes.
Esther 1:1-3, 5, 7-8
Esther 9:22
the same days on which the Jews enjoyed relief from their foes and the same month which had been transformed for them from one of grief and mourning to one of festive joy. They were to observe them as days of feasting and merrymaking, and as an occasion for sending gifts to one another and presents to the poor.
Rambam Laws of Purim 2:15
What is the nature of our obligation for this feast? A person should eat meat and prepare as attractive a feast as his means permit. He should drink wine until he becomes intoxicated and falls asleep in his intoxication. And similarly a a person is obligated to send two portions of meat or two types of cooked food or two types of food to his friend, as it says (Esther 9:22) "and send portions one man to another" two portions to one man.
Shulchan Aruch Orach Chaim 695:2
One is obligated to be intoxicated on Purim to the point where he does not know [the difference] between "accursed is Haman" and "blessed is Mordechai". Rama: Some say it is not necessary to become drunk so much, but rather to drink more than he is used to (Kol Bo), and to fall asleep, and while he sleeps he does not know [the difference] between "accursed is Haman" and "blessed is Mordechai" (Maharil). [There is no difference] between one who has more and one who has less, as long as his heart is directed to heaven.
Aruch Hashulchan 695:3 Rav Yechiel Michel Epstein
But i don't understand, why would the Talmud use the strange language
of 'until he doesn't know the difference'.. it should have just said "one must drink until one falls asleep. therefore we should not assume the Rambam is interpreting the Talmud that way, rather rejecting it! just like Ra"n and Rabenu Efraim. Because the story after it shows its rejection. But the Tur and Shulchan Aruch copied the whole Talmudic statement which is perplexing! Some believe there was a long song which ended with the words 'bless Mordechai curse Haman' and if you drank alot you would fall asleep by the end of the song. Some also noticed that the words are equal in numerology...Tosfot notes that the statement is so long that a bit tipsy person would err in reciting it
completely. One rabbi suggests it is just an added mitzvah not an obligation but the talmud uses the word 'chayav'! One answer is that the Talmud is giving the limit of the possibilities in one's drinking, even to the point of 'not knowing...'. However the Bet Yosef in his great book said in the name of the Orchot Chaim that one must become 'besumi' on Purim, not by getting drunk which causes murder, sexual impropriety etc. and there is not sin worse than this! Rather one should drink a bit more than their usual amount.
Biur Halacha Rabbi Israel Meir Kagan (Chafets Chaim)
We are certainly not commanded to demean ourselves through joy, as we are not commanded to engage in a celebration of frivolity and nonsense, but rather through joy that brings about love of God and thanksgiving for the miracles He wrought for us.