Gemara

(Rav Avira): Chatzvei Shechimei (flasks made from red earth) of Nochrim do not absorb much. It suffices to be Mesachshech them (wash and scrub them with water).

(Rav Papi): For Klei Cheres (earthenware vessels) of Bei Michsi (a place where the earth is hard), it suffices to be Mesachshech them, for they do not absorb much.

(Rav Asi): (Earthenware) cups (in which a Nochri drank wine) are forbidden;

(Rav): They are permitted.

Version #1: If the Nochri drank once, all agree that they are forbidden. They argue about the second time.

Version #2: The first two times, all agree that they are forbidden. They argue about the third time. (end of Version #2)

The Halachah is, the first two times, they are forbidden. The third time, they are permitted.

Question: Why are they (permanently) forbidden?

Answer: The Torah testified that absorptions in earthenware never leave the walls. ("U'Chli Cheres Asher Tevushal Bo Yishaver" - if they could be Kashered, there would be no need to break them.)

74b (Beraisa - Rebbi): For a Gas (winepress), bucket (used to draw wine from the Gas) or funnel, it suffices to dry it.

Rishonim

Rambam (Hilchos Ma'achalos Asuros 11:18): One may not drink from an earthenware cup that a Nochri drank from. If he rinsed it three times it is permitted, for the drops of wine are gone. This is if it is plated with lead the way potters make them, or if it is Mezufas (lined with pitch). If it is (pure) earthenware, it must be rinsed.

Rebuttal (Ra'avad): This is not like our text, not like the Rif's.

Rosh (Avodah Zarah 2:24): Rashi explains that the cups are soft, and the first time wine is put in them they absorb and they are forbidden until wine will be put in them for three days. All agree that if the Nochri drank from them the first or second time, they are forbidden. If he did not drink until the third time, they are permitted.

Rosh (23): If a Nochri drank wine in Klei Cheres of a Yisrael, Rashi says that if the Nochri drank from them the first time, all agree that they are forbidden because new Kelim absorb a lot, and one must do Iruy for three days. This is why people normally put water in new Klei Cheres before using them, so if a Nochri will use them afterwards, there will be no need for Iruy. R. Tam disagreed, for Iruy is not needed for Klei Cheres. It is needed only for bottles, in which they put wine for a long time. For a Gas, bucket or funnel, it suffices to dry it (74b). Drying Kelim of a Gas is like rinsing other Kelim. It is difficult to say that there we discuss when Nochrim initially used the Kelim for water. R. Tam explains that if a Nochri drank from old or new Kelim, if they were rinsed once, all agree that they are forbidden. The Isur is not purged well after only one time. The Halachah is, if they were rinsed twice, they are forbidden. If they were rinsed three times, they are permitted, for everything is purged. We find similarly that Cheres of a Zav or Zavah is Tahor after three times (Zevachim 79b), i.e. after it is rinsed three times from the urine. This is only regarding Cheres cups that are not smooth and the wine clings to them. Wooden cups need not be rinsed three times. I say that R. Tam's proofs are proper to say that Shicshuch is rinsing three times. However, the Gemara is difficult according to this. 'Rav Asi forbids' connotes that the Isur the Gemara was discussing, i.e. Shicshuch is not enough and Iruy is needed. No one mentioned rinsing three times! Also 'if the Nochri drank the first time' does not connote like R. Tam's Perush (if the cup was rinsed only once). Also, why did it mention cups if the same applies to all Kelim? Rather, I hold like Rashi. However, the cups from which they used to drink wine were from a certain kind of earth that absorbed much the first two times, due to the earth. Or, it is because they were not fired well in the kiln. Stam 'cups' refers to cups of this earth. It is the opposite of Chatzvei Shechimei of Nochrim and Klei Cheres of Bei Michsi. Wine is put in them for a long time, but Shicshuch suffices for them because Chachamim know that they do not absorb much. If wine were not put in them for a long time, we would not need to say that they do not absorb much. Even though wine is not put in cups for a long time, they require Iruy because Chachamim know that the first two times they absorb very much.

Kesef Mishneh: The Rambam holds like R. Tam. He explains 'if the Nochri drank from it, how do we fix it? If he rinsed it once...'

Poskim

Shulchan Aruch (YD 135:4): If a Nochri used a Keli Cheres before it was satiated with absorptions, one must fill it and do Iruy, even if it is not Mezufas.

Beis Yosef (DH u'Chlei): Klei Cheres are different, because they absorb much. Rashi explains that the cups are soft, and the first time wine is put in them they absorb and they are forbidden until they are filled with water for three days. The Ran says that R. Chananel holds like Rashi. The Rashba says that R. Chananel and the Ge'onim hold like Rashi, and this is primary. If so, why did Rav Papi says 'wine is not put in for a long time in Chatzvei Shechimei of Nochrim, so Shicshuch suffices? (Note: in our text, Rav Yehudah was lenient about flasks that were stolen and returned because wine is not put in them for a long time, and Rav Avira was lenient about Chatzvei Shechimei of Nochrim because they do not absorb much.) Some say that the case was that Yisre'elim used them first. This is difficult. If so, why does it teach Chatzvei Shechimei of Nochrim and Klei Cheres of (Bei) Michsi? Let it just say that one does not put in Chatzvei and Klei Cheres for a long time! Also, Chatzvei Shechimei of Nochrim connotes that Nochrim used them first. Rather, the Cheres of these is hard and does not absorb much. It is unlike other Cheres. Therefore, even if Nochrim used them first, it is like a wooden Keli.

Shach (11): Most Poskim say that this is even if one does not put in them for a long time.

Shulchan Aruch (ibid): It is satiated from the second use and onwards. Therefore, if the Nochri used it the first two times, one must fill it and pour out the water. If one put water in it three times and afterwards put wine in it, and a Nochri touched it, it is permitted through Shicshuch. If one put water in it twice and then put wine in it, and a Nochri touched it, some say that Iruy is needed. If one put water in it once for a long time, about a quarter of a day, it absorbs water as if water was put in three times.

Shach (12): Even though we say that absorptions never leave a Keli Cheres, since all usage for Yayin Nesech is cold, Iruy weakens the taste of the absorptions.

Shach (13): The distinction between whether or not it was satiated is only if Yayin Nesech was not inside for 24 hours. If Yayin Nesech was inside for 24 hours, in any case one must fill it and do Iruy.

Shach (14): The Shulchan Aruch begins citing the Tur. Why doesn't he say that if one put water in it twice, it is satiated, and then bring the opposing opinion? I say that he holds that the Tur agrees that only wine satiates through two times, but water does not. The Beis Yosef says that Sefer ha'Terumos and Hagahos Maimoniyos explain the Gemara differently, but perhaps all agree about the Halachah. Darchei Moshe understood that they argue.

Bach (7): For Klei Cheres, even if the wine was put in for a long time, if it was already satiated with absorptions from the Yisrael, it needs only Shicshuch. We are stringent about a short time only regarding Kelim of wood, stone, or Cheres that was not satiated. If the wine was not put in for a long time, even if the Keli was not satiated, Iruy is required only if Asur wine was left in for some time.

Shach (15): The Beis Yosef says that if the wine was put in for a long time, it immediately obligates Iruy. I say that if a Klei Cheres was not satiated, even if Isur was put in for a short time it needs Iruy. The Rashba and Tur connote like this.