Commentary for Avodah Zarah 151:23

The Talmud asks—if one opinion holds that when it imparts a worsened flavor the food is permitted, how did the Torah ever prohibit vessels used by non-Jews. The answer is that this prohibition only applies to vessels used that very day—in this case, the taste imparted is not considered to be a worsening flavor.

R. Amram points out that there are contradictory tannaitic sources—one says that the spit and the grill must be heated up until they are white hot, while the other says that it is sufficient to boil them.

R. Sheshet points out that vessels used by Gentiles absorbed prohibited substances and therefore require a more thorough form of kashering. But vessels used in sacrificial worship absorbed permitted substances.
Tomorrow’s sugya will continue this subject.

While it is true that permitted substances were cooked in the Temple vessels, when they discharge taste, that taste is from a substance that is now prohibited. The taste has been in the walls of the vessels for several days and sacrifices become strictly prohibited after one or two days. Thus in both cases, the substance cooked in one of these vessels would have the taste of a prohibited substance.

Rava explains that the word “boiling” does not mean what it seems. Rather, it means rinsing and washing, two verbs used in the context of cleaning holy utensils in Leviticus 6:21.

Abaye rejects Rava’s resolution because rinsing and washing are done with cold water, not hot. He resolves the difficulty by saying that in both cases, both scalding and heating until white hot are required. This is a case of each mishnah providing only partial information.

Rava says that if we thought each mishnah testifies about the other, then two forms of kashering should have appeared in one context and one in the other. This would make it clearer that both are always valid. But one form in each context gives the impression of a difference between them.

Rava explains that with holy vessels there is actually never a case where the taste would sit in the vessel for two days and thereby become “remnant” which is prohibited. If, for instance, a sacrifice is boiled in a vessel on Sunday, it does not become prohibited till Tuesday. But if the vessel is used on Monday, then it removes the taste of Sunday’s sacrifice. And thus there is never any time in which the taste becomes prohibited.

Rava’s resolution above works well if we’re only concerned about shelamim, which can be eaten for two days. But a sin-offering (a hatat) can only be eaten for one day. So the taste of yesterday’s sin-offering is already prohibited when the vessel is used to cook today, making it prohibited.

The Talmud explains that it is not necessary to kasher the vessel by making it white hot in the following circumstance. He cooks hatat today and then, on the same day, he also cooks a shelamim. This will get rid of the taste of the hatat. He then can cook in it hatat tomorrow, and then the taste of that hatat and yesterday’s shelamim will become remnant at the same time, the next day. Then he again cooks in it shelamim on that same day, thereby purging it of the taste of that day’s hatat. As long as one keeps repeating this process, kashering will not be necessary.

If kashering is not necessary, then why should even scalding be necessary. Essentially, as long as one performs this process, one could continuously cook without kashering. This difficulty stands. Tomorrow the final resolution to this thorny problem will be offered.

R. Papa resolves that the two sources refer to different situations. If the pot is encrusted, then it must be made white hot. Scalding will not get off the encrusted taste. If the pot is not encrusted, then scalding is sufficient.

R. Ashi offers the final resolution to the problem, which goes back to the first resolution. The pan in which sacrifices was cooked only needs scalding and not being made white hot. Although when it emits taste, that taste is also forbidden, like yayin nesekh, the taste is just taste. It is not visible. Since the taste is not visible, and when it absorbed the taste the taste was permitted, what it emits is less prohibited. Note that it still requires kashering, just a lesser form.

R. Ashi offers the final resolution to the problem, which goes back to the first resolution. The pan in which sacrifices was cooked only needs scalding and not being made white hot. Although when it emits taste, that taste is also forbidden, like yayin nesekh, the taste is just taste. It is not visible. Since the taste is not visible, and when it absorbed the taste the taste was permitted, what it emits is less prohibited. Note that it still requires kashering, just a lesser form.

The amoraim here explain how the two major forms of kashering are performed.How does one kasher a large pot, one that cannot be boiled inside a larger pot? One makes a rim of dough around its edges and then builds it up so that the water basically boils over. The rim will get hot water splashed on it. This is sufficient to kasher it, for just as the rim absorbed taste by having the forbidden substance splash on it, so it can emit taste in the same way.