Shmos 12:9 – “And it shall be to you as a sign You shall not eat it rare or boiled in water, except roasted over the fire its head with its legs and with its innards.
Gemora: Pesachim 41(a) – Rav Hisda says: [One who cooks/boils] a Pesach sacrifice that is cooked in the hot waters of Tiberias is guilty of a sin because the verse states that it must be roasted.
Torah Temimah Colloquial Translation on Note #89:
The phrasing of the Gemora is not exact – if so, what would be the difference between cooking it in the waters of Tiberias and cooking it in any other hot water? The meaning of the Gemora is that one who roasts the Pesach sacrifice above the waters of Tiberias is liable. [using the hot air emanating from the waters of Tiberias.] This is a sin because the verse requires that it be roasted over a fire. This is exactly what Maimonides writes in Chapter 8, Halacha 10 of the Laws of Pesach, “one who roasts it above the hot waters of Tiberias transgresses since it must be roasted over a fire.”
Note what is written by the Marei Kohen that is appended to the Vilna Shas. The Marei Kohen quotes the Chacham of Jerusalem as asking: how could it be that one is cooking the Pesach sacrifice in the hot waters of Tiberias? Behold, it is forbidden to eat the Pesach sacrifice outside of Jerusalem. Additionally, if one were to bring it to Tiberias, one would be liable for transgressing the prohibition of “taking it out” [of Jerusalem]. Also, if one were to bring the waters of Tiberias to Jerusalem, they would already have cooled down. Further they would be a “kli sheni” and it would not technically be cooking.
The Marei Kohen states that the Sage of Jerusalem did not propose an answer to his question. The Marei Kohen suggests that the Gemora is discussing a time when bamot [small alters for ‘light’ sacrifices] were permitted throughout the land of Israel.
If that were the case, then why would the Gemora discuss it? Something that was in the past, was in the past. Additionally, bamot will never be permitted again the future (as mentioned in Gemora Zevachim 113b). Lastly, Maimonides also mentions this law regarding the waters of Tiberias and he way, in general, is not to discuss bamot for the above reasons. These reasons and others, the answer given by the Marei Kohen seems unlikely.
On the other hand, I am amazed that the comments by Rashi on this issue are not mentioned. Rashi interprets “waters of Tiberias” as being “boiling waters”. On the surface, this comment of Rashi’s seems superfluous. Everyone knows what the waters of Tiberias are. Rather, the point of Rashi’s comment is to state that “waters of Tiberias” refers to boiling waters, in any location. Thus, if one were to find hot springs in Jerusalem, the laws applying to them would be the same as those applying to the waters of Tiberias. Now everything is understandable, the above Gemora Pesachim is referring to boiling waters, wherever they may be found.
In fact, a good proof that the Gemora is accustomed to referring to boiling waters as the “waters of Tiberias” can be found in the aggada of helek (Sanhedrin 108a). That Gemora is as follows: “Rabbi Yochanan states that 3 [types of waters] survived from [Noah’s] flood. “ One of them is the waters of Tiberias. Rashi explains there that the waters of Noah’s flood were boiling and the waters of Tiberias are from those waters. Now, the rabbi stating this view is Rabbi Yochanan and he, himself, states in Gemora Zevachim 113a that the flood did not cover the land of Israel. Since Tiberias is in the land of Israel, it is surprising that Rabbi Yochanan would make this statement. Rather, what we see is that Rabbi Yochanan was using the phrase “waters of Tiberias” to refer to hot springs wherever they might be found throughout the world.
Editor’s Note: The Meshivas Nefesh, a commentary on the Torah Temimah, points out that the Gemora in Pesachim 8a discusses “why are there not found ‘waters of Tiberias’ in Jerusalem?” He also mentions the Yalkut Shimoni in Parshat Baalotcha discusses why there are not ‘waters of Tiberias’ in Jerusalem. I think he does this as a critique of the Torah Temimah statement that if there were to be found such waters in Jerusalem it would be forbidden to cook the Pesach sacrifice using their heat. It seems to me, though, that these quotes actually prove the Torah Temimah’s point that ‘waters of Tiberias’ is a generic phrase referring to hot springs anywhere.