Gemara

8b (Rav): If one slaughtered with a Nochri's knife, he must peel off a layer from the areas cut;

(Rabah bar bar Chanah): It suffices to rinse them.

Suggestion: They argue about whether the place of Shechitah is Rose'ach (very hot, so that absorbed taste in the knife will enter the meat).

Version #1 - Rejection: All agree that it is Rose'ach. This is why Rav requires peeling off a layer. Rabah says that it suffices to rinse. Since the Simanim are busy exuding blood, they cannot absorb tastes exuding from the knife.

Version #2 - Rejection: All agree that it is not Rose'ach. This is why Rabah says that it suffices to rinse. Rav requires peeling off a layer. The pressure of the knife causes its absorbed tastes to enter the meat.

Rav Acha bar Yakov and Ravina argue about a knife used to slaughter a Treifah. One obligates Hag'alah (Kashering in boiling water). The other holds that it suffices to wash it in cold water. The Halachah follows him.

If one has a hard, worn out garment, it suffices to clean it with the garment.

Question: The stringent opinion should obligate Hag'alah even for a knife used to slaughter a Kosher animal. It absorbs Isur, i.e. Ever Min ha'Chai (a limb of a living animal) before the Shechitah is completed!

Answer: It absorbs only when it gets warm, which is when the Shechitah finishes. Then, the meat is permitted!

111b (Shmuel): A knife used to slaughter may not be used to cut hot meat.

Version #1: If it will be used to cut cold meat, one must rinse it.

Version #2: It may be used to cut cold meat without rinsing.

112b - Question (Rav Acha brei d'Rav Ika): Does Shmuel really permit (juice that exudes from roasted meat, once smoke came up)? He forbade bread over which meat was cut (even if smoke came up)!

Answer (Rav Ashi): The pressure of the knife causes blood to exude (which would not exude through roasting).

Rishonim

Rambam (Hilchos Ma'achalos Asuros 6:20): If a knife was used to slaughter, one may not use it to cut hot food until he makes it glowing hot, sharpens it, or sticks it 10 times into hard ground. If he cut hot food with it before doing so, it is permitted. L'Chatchilah, he may not use it to cut radishes or sharp foods. If he rinsed it or cleaned it with a cloth, he may cut cold food with it, but not hot food.

Rosh (Chulin 1:9): In one version, we are stringent due to pressure of the knife. This was Rivam's source to require removing a Kelipah from everywhere cut with the knife used to remove the Chelev. Even though it is cold, it absorbs due to pressure of the knife. There is no proof from here. Even though Beis ha'Shechitah is cold, it is warm. Pressure of the knife does not cause absorptions in something totally cold. The Gemara says that the knife absorbs only at the end of Shechitah, when Beis ha'Shechitah is warm.

Rosh (Chulin 1:10): If one slaughtered a Tereifah with a knife, it suffices to wash it in cold water. Rashi explains that even though we hold that Beis ha'Shechitah is cold, this is only for a permitted knife. It is hard, so it becomes forbidden through absorptions only through Resichah. Meat is soft, and absorbs easily. In Avodah Zarah (76b) we require Ne'itzah (sticking it in the ground) to permit cutting cold food. That refers to a knife used constantly to cut Isur. The fat sticks to it, and comes out only through Ne'itzah. The Amora'im argue only about using it for Shechitah, but one may not use it to cut hot food (even if it slaughtered a Kosher animal), even if he rinsed it (111b). One version requires rinsing even for cold food. The other does not; it suffices to wipe it with a hard cloth. One may slaughter with a knife used to slaughter a Kosher animal. Even if it is dirty with blood, in any case there is much blood in Beis ha'Shechitah. Beis ha'Shechitah does not absorb, for the Simanim are busy exuding blood, and it is smooth. It does absorb fat of a Tereifah. Nowadays the custom is that butchers clean the knife on the animals' hair between one Shechitah and another. The hair is hard, like a hard cloth.

Poskim

Shulchan Aruch (YD 10:2): If a knife was used to slaughter a Kosher animal, even if it is dirty with blood, one may slaughter again with it, but one may not cut hot meat with it. One may cut cold meat with it after rinsing it.

Beis Yosef (DH Sachin): Tosfos and the Rosh rule like the opinion that requires rinsing. They hold that the Gemara discusses rinsing the knife, unlike Rashi, who says that it discusses rinsing the meat after it is cut.

Taz (9): Toras ha'Adam explains that Beis ha'Shechitah is hot enough to absorb through pressure of the knife, even if it is not dirty with blood, unlike Rashi. He proves this from a knife used to slaughter. One may not use it to cut hot food. Since Beis ha'Shechitah is slightly Rose'ach, it causes the knife to absorb blood. Even so, one may slaughter with it, for while the Simanim are busy exuding blood, they do not absorb.

Taz (10): The Shulchan Aruch connotes that one need not rinse or clean the knife. Maharshal holds like this. This is difficult, for the Gemara said that a knife does not absorb until the end of Shechitah, when it is hot, and then it is not Ever Min ha'Chai. However, what is intact on the knife forbids without heat. Even the one who holds that Beis ha'Shechitah is cold requires rinsing a knife used to slaughter a Tereifah! We should say the same about Ever Min ha'Chai on the knife, even if it was Kosher! It seems that only if the concern is lest absorbed taste be absorbed in the Simanim, then we ask that the same applies to a Kosher animal. If the concern is only for what is intact on the knife, there is no concern for Ever Min ha'Chai. There is no substabce of Isur. It is mixed with blood. Since the Simanim are busy exuding blood, also Ever Min ha'Chai is not absorbed. We were concerned for fat of a Tereifah, for it sticks to the knife, (and it is forbidden) even at the end of Shechitah. (What sticks to the knife beforehand is washed away.)

Shach (13): One may not cut hot food even if the knife was used to slaughter only once.

Shach (14): If one cut hot food without Kashering, the Tur and Shulchan Aruch did not say what is the law. It seems that b'Di'eved it is permitted after rinsing well. The Rambam says so. Even the Rashba, who holds that it absorbed and emits, forbids only Kedei Kelipah. It is no worse than the knife of a Nochri with fat on it.

Taz (11): If one cut cold food without rinsing the knife, he rinses the food.

Shach (15): Rinsing suffices to use it for cold food even if he slaughtered many times with it. This is unlike a knife used often for Treifos. Here the only Isur is blood. It is smooth, so not much is absorbed.

Shach (16): The Tur and Shulchan Aruch did not say that one may clean with something hard. It seems that this suffices only (in Sa'if 3) when the Simanim are busy exuding blood. The Rosh says that according to the opinion that one must rinse the knife (and this is the Halachah), cleaning with a garment does not suffice. The Maharshal says that there is a mistake in the Rosh's text; really, a garment helps like rinsing. There is no justification to say that the text is mistaken. The Ro'oh equates a garment with rinsing, but the Rashba rejected this. The Gemara equates them only regarding Shechitah.

Rema: If one wants to do Hag'alah to permit using it for hot food, it suffices to do Hag'alah through Iruy, even though this is not like a Kli Rishon.

Taz (12): The Tur brings from the Rashba that this is because Beis ha'Shechitah is not fully Rose'ach.

Gra (9): Anything that absorbs only Kedei Kelipah, Iruy suffices to kasher it.

Minchas Shlomo: Amora'im argue about whether Beis ha'Shechitah is cold or Rose'ach. One version holds that all agree that it is cold. Therefore, a Shechitah knife does not absorb blood, and one may use it to cut hot meat after rinsing it or cleaning it well. Even if one slaughtered a Tereifah, it does not absorb from the meat. However, Tosfos permits only to slaughter again with the knife, for there is much blood in Beis ha'Shechitah, and it does not absorb (from the knife) because the Simanim are busy emitting blood. One may not cut hot meat even if he slaughtered only Kosher animals. The Rema says that Iruy suffices because the heat of Beis ha'Shechitah is not truly like a Kli Rishon that is Yad Soledes Bo, which cooks and causes absorptions in the entire knife. There is merely concern lest it absorbed a little. Surely it does not absorb more than Kedei Kelipah. Even though Iruy does not cook like a Kli Rishon, it caused absorptions Kedei Kelipah. The Shach says that b'Di'eved, if one cut hot meat after rinsing but without Hag'alah, we do not forbid the meat. Even those who disagree hold that Beis ha'Shechitah is not truly Rose'ach. It is only slightly Rose'ach. Therefore, together with pressure of the knife, we are concerned lest it absorbed a little. This shows that we hold that Beis ha'Shechitah is cold. Even the opinion that it is Rose'ach holds that the knife absorbs only at the end of Shechitah, for then Beis ha'Shechitah is Rose'ach. All agree that it is cold before this, and the knife does not absorb at all. The Poskim did not distinguish between birds and animals. The Tur (YD 105) brings from the Rashba that we do not distinguish heat of Beis ha'Shechitah from heat of a fire. The Ritva (Shabbos 42a DH ul'Inyan Beli'as) says that even according to the opinion that Beis ha'Shechitah is Rose'ach, it is not Yad Soledes Bo. Rosh Yosef says that if it were Yad Soledes Bo, all would agree that it is Rose'ach. They argue about whether absorptions occur even though it is not Yad Soledes Bo.