Gemara

R. Shimon learns from a Gezeirah Shavah "wine and strong drink" from Nazir to the Isur to serve in the Mikdash when drunk;

Just like only wine is forbidden to a Nazir, but not other intoxicating drinks, also the Isur for a Kohen to serve is only after drinking wine, but not after drinking other intoxicants. This is unlike R. Yehudah;

(Beraisa - R. Yehudah): If one ate figs of Ke'ilis or drank honey or milk and entered the Mikdash, he is liable (to death at the hands of Heaven).

Kesuvos 10b (Rav): One who ate dates may not give Hora'ah.

Dates temporarily befuddle, just like wine.

One who drinks a Revi'is of wine may not give Hora'ah.

Eruvin 64a (Rav Yehudah): One who drinks a Revi'is of wine may not give Hora'ah (the Rif's text - he may not pray).

(Rabah bar Rav Huna): A Shasuy (one who drank) may not pray; if he prayed, it was valid. A Shikor (one who is drunk) may not pray; if he did, it was an abomination.

(R. Aba or R. Menasiya): A Shasuy is one who can speak (properly) in front of the king. A Shikor is one who cannot.

64b (Rami bar Aba): Walking a Mil (2000 Amos, about a kilometer) or sleeping any amount negates the effects of wine.

(Rav Nachman): This is when he drank only one Revi'is. If he drank more, walking or sleeping will worsen his condition!

Question (against Rami bar Aba - Beraisa): R. Gamliel was riding on a donkey. A man wanted to permit a vow. R. Gamliel told him 'I drank a Revi'is of Italki wine. Follow me on the road until the wine wears off.' After three Mil, R. Gamliel permitted the vow.

Answer #1: Italki wine intoxicates more, so one must go further to become sober.

Question: Rav Nachman taught that if one drank more than a Revi'is, walking or sleeping will worsen his condition! (A Revi'is of Italki wine is like more than a Revi'is of regular wine.)

Answer: Walking worsens his condition, but riding sobers.

Answer #2 (to Question (8)): To sober up one must walk one Mil or ride three Mil.

Kerisus 13b (Beraisa - R. Elazar): We expound (as if it said) 'Yayin Al Tesht v'Shechar Al Tesht' - do not drink in an intoxicating way. If he paused while drinking, or added any amount of water, he is exempt.

(Rav): The Halachah follows R. Eliezer.

Rav Acha of Hutzal came to Rav Ashi (on Yom Tov) to permit a vow

Rav Ashi: Go, and return tomorrow. Rav would not expound on Yom Tov (after drinking) until the next day, lest he be drunk.

Rav Acha: But Rav ruled that the Halachah follows R. Elazar, and you mix your wine with water!

Rav Ashi: R. Elazar exempts only when he drank exactly a Revi'is (of diluted wine). I drank more than a Revi'is.

Rishonim

Rif and Rosh (Eruvin 19b and 6:5): Walking a Mil or sleeping any amount negates the effects of wine. This is when he drank only one Revi'is. If he drank more, walking or sleeping will worsen his condition!

Hagahos Ashri: Riding sobers even if he drank more than a Revi'is. Walking a Mil, or riding three Mil wears off a Revi'is of wine.

Rambam (Hilchos Bi'as Makdish 1:3): Just like a drunk Kohen may not enter the Mikdash, a Shasuy (one who drank) may not give Hora'ah - "(Yayin v'Shechar Al Tesht...) u'Lhoros". Even if one's mind was slightly befuddled due to eating dates or drinking milk he may not rule.

Ri Korkus: The Rambam forbids only when his mind was befuddled. If not, we must say that even eating one date forbids, for no Shi'ur was given! However, the Torah forbids one who drank a Revi'is of wine in every case. This is why the Rambam forbids a Shasuy to give Hora'ah, and regarding other matters he forbids one who is intoxicated. Alternatively, the Rambam taught about other matters that it is forbidden only if he is intoxicated, and the same applies to wine. Alternatively, drinking a Revi'is always intoxicates somewhat.

Question (Radvaz): Nowadays, all judges drink several Reviyos, yet they do not refrain from Hora'ah! Perhaps this is because they drink during the meal, and this does not intoxicate. Nevertheless, a judge or Chacham should refrain from Hora'ah unless he knows that his mind is clear.

Terumas ha'Deshen (42, cited in Beis Yosef OC 99 DH uvi'Terumas): It would seem that we should distinguish between our wine and the strong wine of the Gemara, which intoxicated. However, the SMaG, SMaK and Rosh forbid one who drank a Revi'is from giving Hora'ah. Surely they discuss nowadays! Perhaps because we do not know the Shi'ur (of our wine that equals a Revi'is of the Gemara's wine), and surely drinking enough of our wine intoxicates, they did not give a different Shi'ur, but really a Revi'is of our wine does not forbid.

Rashba (1:247): We find that Rav would not give Hora'ah the entire day after drinking. Perhaps this refers only to Yom Tov, when people drink much. If he already deliberated and now gives the final verdict, it is permitted.

Shach (YD 228:19): This is Stam. If one knows that he has sobered up, he may give Hora'ah.

Poskim

Rema (YD 242:13): One must be careful not to give Hora'ah after drinking wine or other intoxicants.

Bach (DH Kosav) and Shach (21): Tosfos (Eruvin 65a DH b'Tzar) cites the Yerushalmi (Berachos 5:1), which forbids Hora'ah when one is pained and his mind is unsettled. It learns from 'b'Tzar Al Yoreh.' (Either this is from Sefer Ben Sira, or it is comprised of partial verses.) It is Midas Chasidus to avoid ruling when there are other distractions (mentioned in Eruvin), but it is not forbidden even l'Chatchilah.

Shulchan Aruch (OC 99:2): Walking a Mil or sleeping any amount negates the effects of wine. This is when he drank only one Revi'is. If he drank more, sleeping or walking will worsen his condition. However, riding sobers.

Magen Avraham (1): SMaK (133) says that wine drunk during the meal does not intoxicate, and some say that even wine drunk before the meal does not intoxicate. However, Hagahos SMaK (133:1) says that one who ate a Seudas Mitzvah, such as Seudas Yom Tov should not give Hora'ah, even if he drank only during the meal.

Questions (Bach DH Mashma and Taz 2): According to Rashi, riding is not an exertion, therefore it does not sober as quickly as walking for one who drank a Revi'is, but it does help for one who drank more than a Revi'is. The Tur cites BaHaG to say that riding sobers, but did not say that a Mil is not enough for a Revi'is, and that three Mil help for more than a Revi'is! The Rif and Rosh did not distinguish riding from walking!

Answer #1 (Taz): It seems that BaHaG explains that even though it says 'now that we said...', we do not retract from the difference between Italki and regular wine. R. Gamliel did not mention that the wine was Italki for naught! The Gemara merely shows that we could give a different answer for Rami bar Aba. Riding one Mil sobers even one who drank more than a Revi'is of regular wine. Even though it is not clear that this is correct, we may be lenient about a Safek mid'Rabanan (praying when drunk). The Rif and Rosh are stringent to say that riding is no better than walking.

Answer #2 (Bach ibid. and DH v'Nir'eh): The Tur and Shulchan Aruch hold that there is no fixed amount needed to wear off more than a Revi'is of wine or a Revi'is of Italki wine. This is why R. Gamliel did not tell the man how long he will need to go. It just happened that after three Mil the wine wore off. Perhaps the Rif, Rambam and Rosh rule like the Sugya in Kerisus that does not distinguish Italki wine from regular wine, or riding from walking.

Chavos Ya'ir (177): Surely, the conclusion does not distinguish different kinds of wine. If a Revi'is of Italki wine were like more than a Revi'is of Stam wine, slightly less than a Revi'is of Italki wine would be like a Revi'is of Stam wine. R. Gamliel had drunk Italki wine, yet he was concerned only because he had a Revi'is.

Magen Avraham (4, citing Kesef Mishneh Bi'as Makdish 1:5): A large amount of sleep helps even for more than a Revi'is.

Mishnah Berurah (12): One Mil suffices whether he walks or rides. Some require three Mil if he rides.

Mishnah Berurah (15): If he drank a lot, three Mil will not suffice to wear it off.

Kaf ha'Chayim (19): To suppress intoxication one can drink vinegar or eat cabbage or bitter almonds.

Aruch ha'Shulchan (YD 242:34): The Gemara said that riding, i.e. directly on an animal, wears off wine. Riding in a wagon does not wear off wine.