Riva's text: The Riva's text did not say "Hachi Nami Mistabra." Rather, it says "Ta Shma Sheloshah Devarim", for this is not a better proof than what we brought before.

Tosfos: I say that [the text can say this, for] we bring a better proof. The first Beraisa did not mention letting blood for Serunchi (diphtheria), so it was a weak answer to say [that Chachamim said "these"] to exclude it;

The second Beraisa is a good support [for the above answer]. We assume that "these" refers to the last two matters that R. Yishmael mentioned, and excludes letting blood for Serunchi, which was taught first!

Suggestion: We should delete Hachi Nami Mistabra from the text, for whenever the Gemara says so, the support remains [but here it is rejected]!

Rejection: This is not a reason to delete it. In Kidushin (26b), regarding the case of a man from Madon [who wanted to give a gift], the Gemara says Hachi Nami Mistabra, but the support is rejected! 1. (Note: presumably, the Riva holds like the opinion in Tosfos there that the support remains.)

Also in Bava Metzi'a (46b), it says Hachi Nami Mistabra even though the support is rejected, in the Sugya of coins cannot be made Chalipin, according to Rashi.

Explanation: Even when it is possible to have a Nochri do the Chilul Shabbos, it is a Mitzvah for a Yisrael to do it, lest the Nochri be lazy and not do it, and danger result.

Question: We taught the bigger Chidush first! Since even extinguishing is permitted, all the more so interrupting!

Answer #1: This permits bringing Kelim through Reshus ha'Rabim to use them to interrupt;

One might have thought that only extinguishing is permitted, but not to bring Kelim full of water through Reshus ha'Rabim, for this involves two [Melachos] - Hotza'ah and Hachnasah, and Geram (causation of) extinguishing.

Answer #2: One might have thought that we permit extinguishing more, for it is clearer that it will save;

Perhaps before one brings the Kelim, the fire will pass, and he was Mechalel Shabbos needlessly! "U'Mafsikin" teaches that this is not so.

Explanation: It seems that this means that all separated to another Chatzer, and left there as well, and only one remained, on whom the house caved in.

Suggestion: Perhaps they separated to another Chatzer, and did not leave there!

Rejection: If so, the latter Chatzer is no different than the first Chatzer!

Explanation: "Some separated" means that only one went from here to another Chatzer. (If at least two separated, surely one of them was a Yisrael, so we would be Mechalel Shabbos.)