Gemara

(Abaye): It says "Ason (fatality)" regarding acts of man (fighting) and regarding acts of Shomayim (Yakov's concern for Binyamin). Just like liability to die through man (Beis Din) exempts (from paying), liability to die b'Yedei Shomayim exempts.

Question (Rav Ada bar Ahavah): Why do you assume that Yakov was concerned for Tzinim and Pachim (colds and heatstroke), i.e. acts of Shomayim? Perhaps it refers to thieves and lions, acts of man!

Objection #1: Colds and heatstroke are not in the hands of Heaven!

(Beraisa): All is in the hands of Heaven, except for colds and heatstroke.

Objection #2: Lions and thieves are not in the hands of man!

(Rav Yosef): Even though the Sanhedrin ceased after Churban Beis ha'Mikdash, the four death penalties are still meted out;

Someone liable to be stoned is trampled by an animal. Someone liable to death by the sword is killed by bandits...

Retraction: Rather, lions and thieves are b'Yedei Shomayim. Colds and heatstroke are due to man.

Bava Metzi'a 107b (R. Chanina): "V'Hesir Hash-m Mimecha Kol Choli (He will remove from you all illness)" refers to the cold;

(R. Chanina): "Tzinim Pachim...Shomer Nafsho Yirchak Mehem" - whatever befalls a person is decreed by Heaven, except for chills and fevers (which is from his lack of caution).

Bava Basra 144b (Mishnah): If brothers inherited together and one of them fell sick, he pays for his own cure.

(Ravin): This is only if he got sick through negligence, but if it was Ones, they share the cost equally.

A case of negligence is like R. Chanina taught:

Shabbos 32a: Men are judged when they pass over a bridge, or anything similar (dangerous places).

R. Yanai would check a ferry (for leaks) before going on it. This is like he taught elsewhere:

(R. Yanai): One should not go in a place of danger, expecting a miracle. Perhaps a miracle will not be done for him; even if a miracle is done, it diminishes from his merits.

(R. Chanin): He learns from "Katonti mi'Kol ha'Chasadim umi'Kol ha'Emes" (Yakov's merits were reduced through the miracles Hash-m did for him).

(Tana d'vei R. Yishmael): "Ki Yipol ha'Nofel Mimenu" - he is called 'ha'Nofel' even before he fell, for accidents were decreed from the Creation. However, (one must build a railing around his roof, for) good things happen through virtuous people, and bad things happen through unworthy people.

Rishonim

The Rif and Rosh (Bava Basra 67b and 9:12) bring the Gemara in Bava Basra.

Rosh: In a Tosefta (10:2), R. Shimon ben Gamliel says that if the cost of the cure is limited, he pays for his own cure. If it is unlimited, they share the cost equally

Ramban (Bava Basra 144b DH v'Ha): If the cost is unlimited, it is like food (therefore, they share the cost). We find this regarding a widow. One could distinguish, but we do not argue with R. Shimon ben Gamliel based on our reasoning, since the Halachah follows him in another case.

Rambam (Hilchos Sheluchim v'Shutafim 8:7): If one of the brothers (who inherited together) fell sick and was healed, they share the cost equally. If he fell sick through negligence, e.g. he walked through snow or in the sun in summer until he got sick or similar matters, he pays for his own cure.

Lechem Mishneh: It seems that the Rambam does not distinguish whether or not there is a limit to the cure.

Rashi (Shabbos 32a DH mi'Sheshes): "Korei ha'Doros me'Rosh" - from the beginning was revealed to Hash-m the deeds of all generations and their punishments.

Tosfos (Megilah 25a DH ha'Kol): In Kesuvos (30a) it says everything is in Hash-m's hands except for except for colds and heatstroke. That refers to things that occur to man, but Yir'as Shomayim depends on the person. This is why one may not take credit for his Chachmah, wealth or might, only for his Yir'as Shomayim (Yirmeyahu 9:22).

Tosfos Kesuvos 30a DH ha'Kol b'Yedei): Some say that 'Tzinim Pachim' is one matter, i.e. colds that are like traps for people. This is wrong, for Avodah Zarah 3b applies this to dying from sunstroke.

Question: Shabbos 32a says that a person is forbidden to put himself in danger. One may not walk under a leaning wall (it is prone to fall). This shows that a person can guard himself from mishaps!

Answer (Tosfos, ibid.): One can guard himself from negligence. Certainly a person can kill himself, but when there is a decree from Hash-m, he cannot guard himself. Colds and heatstroke are never sent against a person's will. He can always guard himself from them.

Question: A Medrash says that Rebbi blessed Antoninus that Hash-m save him from heatstroke, and this was a proper Berachah, for it says "Ein Nistar me'Chamaso"!

Answer (Tosfos, ibid.): This refers to one who must travel on the road or in war. Others can stay in a stone house or cellar.

Question: We expounded (Bava Basra 144b): "Hash-m will remove from you all illness" to refer to the cold!

Answer #1 (Tosfos, ibid.): He will warm the world or give you clothing, so you will not need to be careful/

Answer #2 (Tosfos Bava Basra 144b DH Chutz): He will give you understanding to avoid the cold.

Tosfos (Bava Basra 144b DH ha'Kol): Even though mishaps such as lions and thieves are decreed from Shomayim, a person can choose to throw himself into a fire or river and kill himself, even though it was not decreed.

Poskim

Shulchan Aruch (CM 177:2): If one of the brothers (who inherited together) fell sick through negligence, if the cost of the cure is limited, he pays for his own cure. If it is unlimited, they share the cost equally. If he became sick through Ones, even if the cost is limited they share the cost equally. Before he is cured they can tell him to divide the estate.

Beis Yosef (DH umi'Lishna): The Tosefta explains the Mishnah, i.e. when he fell sick through negligence. If he became sick through Ones, in any case they share the cost equally. Tosfos and R. Yerucham explicitly say so. Why did the Tur explain oppositely? Perhaps he had a different text in the Tosefta.

Rebuttal (SMA 3 and Drishah 3): The Beis Yosef assumes that the Tosefta explains the Mishnah like Ravin, when he fell sick through negligence. The Tur and Tosfos explain otherwise (this is explicit in Piskei Tosfos 321). It is unreasonable that others should share the cost in this case, even if it is unlimited! Rather, Ravin explains the Mishnah to be when he fell sick through negligence, and the brothers do not share the cost even if it is unlimited. The Tosefta explains the Mishnah to be when he fell sick through Ones, and they share the cost if it is unlimited. Indeed, the Ran and R. Yerucham explain like the Beis Yosef.

Defense (Shach 3): Tosfos holds like the Beis Yosef says. Surely what is in Piskei Tosfos is a mistake. Perhaps there is a mistake also in the Tur, for in the Tur's Piskei ha'Rosh he explains like the Beis Yosef. The Rif, Rambam and other Poskim did not bring the Tosefta. However, it seems that they relied on what they wrote regarding a widow, in which they distinguish between limited and unlimited.

Shulchan Aruch (ibid.): Falling sick through negligence is going in the snow in winter or in the heat in summer or similar matters.

SMA (4): We do not distinguish whether he walks through snow or rides in a wagon, for the Gemara did not distinguish.

Rema: Some say oppositely, that if he fell sick through negligence, the brothers never share the cost, and if he fell sick through Ones, if the cure is limited they share it equally.

Tzitz Eliezer (5:Ramat Rachel 20): The Ibn Ezra and R. Bechayei say that doctors are authorized to heal only illness caused by people. This is not Chazal's opinion. One may and should use doctors for all maladies. One who relies on Hash-m to heal him miraculously is a Chasid Shoteh, and he will be punished. Everything is in Hash-m's hands except for except for colds and heatstroke. The same applies to taking medicines that, according to nature, heal various illnesses.