(Beraisa - R. Yehudah): "Chatas" teaches that Chatas requires Merikah u'Shtifah (scouring and rinsing). "Kodesh Kodoshim Hi" includes all Kodshim. "Osah" excludes Terumah.

Question: Is it really true that Merikah u'Shtifah does not apply to Terumah?!

(Beraisa): One may not cook Chulin in a pot in which Terumah was cooked. If Chulin was cooked in it, if it absorbed the taste of Terumah, only a Kohen may eat it.

Answer #1 (Abaye): If Kodshim was cooked in part of a Keli, the entire Keli requires Merikah u'Shtifah. Regarding Terumah, only that part requires Merikah u'Shtifah.

Answer #2 (Rava): Regarding Kodshim, water must be used for Merikah u'Shtifah. Regarding Terumah, even wine or mixed wine may be used.

Answer #3 (Rabah bar Ula): Regarding Kodshim, we require Merikah u'Shtifah in cold water in addition to Hag'alah (Kashering in boiling water). Regarding Terumah, Hag'alah is sufficient.

Question: This is like the opinion that Merikah u'Shtifah is in cold water. According to the opinion that Merikah is in hot water, and Shtifah is in cold water, how can we answer?

Answer: Kodshim requires an extra Shtifah.

Rambam (Hilchos Chametz 5:23): If Kelim of metal or stone were used with hot Chametz in a Keli Rishon, e.g. pots and pans, he puts them in a big Keli and fills it with water and boils water inside it until they emit (all absorbed taste). Then we rinse them in cold water and use them for Matzah.

Hagahos Maimoniyos (2): Rav Nehilai Gaon wrote that when we remove the Kashered Keli from the water, we pour cold water on it immediately. Sefer ha'Terumah explains in the name of Ri that we learn this from Zevachim. Merikah is in hot water and Shtifah is in cold water.

Magid Mishneh: Some say that he rinses due to the Gemara in Zevachim. Some say that it is to remove the Chametz. The Ge'onim and Acharonim require Shtifah, like the Rambam says.

Ramach: Why do we rinse it? Regarding Chametz, there is no extra verse! If it is like some Meforshim say, because after the water ceases boiling, it emits (its absorptions back into the Keli), the Rambam did not explain this well.

Rosh (Avodah Zarah 5:36): People are accustomed to pour cold water on a Keli after Kashering it. How does this help? If it is to rinse off the water that absorbed what the Keli emitted, lest it be reabsorbed, this does not help. The moment it leaves the boiling water, it reabsorbs. It is impossible to pour cold water on it the moment it leaves the boiling water. Further, even while it is in the boiling water it reabsorbs what it emitted! This is why we require 60 times as much water (as the volume of the Isur that could be inside). A support for the custom is Zevachim 96b, in which we say that Kodshim requires an extra Shtifah. This implies that Terumah requires one Shtifah, and Kodshim requires two. Shtifah is in cold water.

Tosfos (Avodah Zarah 36a DH mi'Kan): The custom is to put the Keli in cold water after Hag'alah. What is the reason? It is not because in Zevachim we say that Merikah is in hot water, and Shtifah is in cold water. That is only for Kodshim, but not for Terumah (and all the more so, not for Chulin)! Some say that it is because we say that Kodshim requires an extra Shtifah. 'Extra' connotes that Terumah requires one Shtifah, and Kodshim requires two. However, Rashi explained that Kodshim requires one, and Terumah does not require at all. Therefore, we must find a reason for the custom.

Sefer ha'Orah (1:81): Rav Hai Gaon says that one must cast the water out of the Keli while it is boiling, lest it cool off in the Keli and be absorbed. He rinses it immediately in cold water. Even small Kelim must be rinsed when they are boiling.

Tosfos (96b DH Lo): For Terumah, after Hag'alah one need not rinse in cold water. The same applies to Kelim Kashered from Isur. Even so, the custom is to rinse them.

Me'iri (Pesachim 30b DH Kol): Any Keli Kashered through Hag'alah must be rinsed afterwards to remove the filth of the emissions. This is not required for a Keli that requires Libun (making it glowing hot).

Shulchan Aruch (OC 452:7): The custom is to rinse a Keli in cold water immediately after Hag'alah.

Tur: Rashi said in a Teshuvas (259) that immediately after Kashering, while the water is still boiling, one must rinse off the hot water, lest it be reabsorbed. Rav Hai Gaon said similarly, and this is the custom, but not lest the water be reabsorbed. This is not a concern, like I explained above. Rather, it is the custom.

Tur (YD 121): After Hag'alah, we rinse the Keli the way we rinse a cup. The Ri says that even if it was not rinsed immediately, it is not forbidden, for it does not absorb again. In any case the custom is to rinse it immediately, and it is proper to do so.

Beis Yosef (YD 121 DH u'Mah): Tosfos and the Rosh said that there is no use to rinsing, so if it was not done the Keli is not forbidden.

Drishah (YD 121:4): We can say that the Ri means that it does not absorb Isur again, for there is 60 times as much as the Isur, or the Isur is not a Ben Yomo, so it is Pagum.

Prishah (3 DH Ela): There is no need to rinse immediately. The custom is to rinse it immediately, and it is proper to do so.

Bach (YD 121:7): It seems that we must rinse it lest moisture of the water used to Kasher remain on it; the water is forbidden. One must rinse it immediately, lest he forget if he does not do so at the time of Kashering.

Mishnah Berurah (34): We rinse off the hot water, which has absorptions of Chametz, lest the Keli absorb it. In any case, b'Di'eved if he did not rinse at all there is no concern, for we Kasher before Chametz is forbidden, or it is not a Ben Yomo, or there is 60 times as much as water as absorptions.

Darchei Teshuvah (121:45): Mishkan Betzalel (40:68, 211) says that one who does Hag'alah from Isur must be concerned for the opinion of the Ge'onim and rinse the Keli in cold water afterwards. This is Me'akev even b'Di'eved. If he merely Kashers from dairy to meaty or vice-versa, one may be rely on the lenient opinion that it need not be rinsed.

Rebuttal (Shevet ha'Levi 6:115:5): He should not have cited this opinion. Surely it is not Me'akev if he Kashered properly. We do not reckon with an individual's opinion against the accepted majority.

Yabia Omer (4 OC 41:11): Ashkenazim Kasher glass Kelim. We rinse a Keli in cold water after Hag'alah. Regarding pyrex, if one does so it is prone to shatter. According to those who say that the source is from Zevachim, one need not rinse immediately. Since one cannot rinse pyrex right after Hag'alah, he should wait until it cools off and then rinse it. However, according to Rashi's reason that we are concerned lest the Keli absorb, one must rinse it immediately. However, almost all the Poskim say that this is not the reason, just it is the custom (like Kodshim). If so, one may be lenient about pyrex. The Acharonim agree that it is not Me'akev b'Di'eved at all; regarding these glass Kelim, it is like b'Di'eved. It is better if they are put in boiling water three times. If one can rinse it (immediately - PF) in lukewarm water, it is good to do so.