WE ARE MORE STRINGENT ABOUT DANGER THAN ISUR [danger: Safek]
(Rav Huna): If a wolf took the innards of a slaughtered animal, and returned them punctured, we are not concerned lest there was already a hole where the wolf bit.
Question (Beraisa): If one saw a bird pecking at a fig, or a mouse making holes in a watermelon, we are concerned lest there was already a hole there (from a snake), and the food may not be eaten.
Answer (Rav Huna): We are more stringent about danger than about prohibitions!
Question (Rava): What is the difference? In both cases, we are stringent about a Safek!
Question (against Rava - Rav Ashi - Beraisa): If a flask (with water to be sanctified with ashes of the red heifer) was left open and was found covered, it is Tamei. We assume that a Tamei person covered it;
If it was left covered and was found open, the water may not be sanctified with ashes of the red heifer if a weasel can drink from it (i.e. it is not hanging in the air). According to R. Gamliel, we are concerned even if a snake can drink from it.
(R. Yehoshua ben Levi): In the Reisha we are concerned for people. In the Seifa we are concerned for rodents, because it is the way of rodents to expose things, but not to cover them.
Regarding exposed water, we are concerned lest a snake drank from it (even if it was exposed from the beginning, and there is no evidence that anything happened at all)!
Conclusion: We are more stringent about danger than about prohibitions.
(Mishnah): Three liquids are forbidden if they were exposed: water, wine and milk.
This is if they were exposed for the time of a snake to come, drink and return to its hole.
Avodah Zarah 12b: One may not put his mouth next to a pipe and drink, due to danger. He might swallow a leech.
(Beraisa): One may not drink directly with his mouth, or by holding the water in one hand, from rivers or lakes (for he cannot properly check it for leeches). If he does so (and dies), he is responsible for his own death.
(Beraisa): One may not drink water at night (when he cannot see), for this is dangerous. If he does so, he is held accountable.
We are concerned for a Shed responsible for Sanverim (blindness).
Berachos 3a (Beraisa): There are three reasons why one should not enter a ruin: it may cause suspicion, the ruin might collapse, and due to Mazikin (damaging spirits).
Shabbos 32a: Men are judged when they pass over a bridge, or anything similar (any place of danger).
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. And even if a miracle is done, it diminishes from his merits.
Rosh Hashanah 16b (R. Yitzchak): Walking under a leaning wall calls attention to one's sins.
Bava Kama 91b -R. Chanina: My son died only because he cut a fig tree prematurely.
Rif and Rosh (Avodah Zarah 10b and 2:13): The Yerushalmi says that one must be concerned for what people are concerned for. One may not put coins in his mouth, or bread under his underarm, or a cooked food under the bed, or insert a knife into an Esrog or radish. All sweat is lethal poison, except for sweat of the brow.
Ran (10b DH Asur): One may not put coins in his mouth because everyone touches them, and some people are sick and the filth clings to the coins. This is harmful to put in one's mouth. One may not put bread under his underarm, for it is a filthy place. One may not put a cooked food under the bed, for Ru'ach Ra'ah dwells on it. One may not insert a knife into an Esrog or radish, for it is not noticeable, and someone might sit on it and it will enter him.
Rambam (Hilchos Rotze'ach 12:4): One may not put coins in his mouth, lest there is on them dry saliva of a leper, or sweat. All sweat is like poison, except for sweat of the brow.
Rambam (5): One must not put his hand under his underarm, lest he touched a Metzora or harmful potion, for hands touch things.
Ra'avad: The Yerushalmi forbids putting meat or bread under his underarm, due to sweat.
Rambam (6): One may not insert a knife into an Esrog or radish, lest one fall on the balde and die. Similarly, one may not pass under a leaning wall or on a rickety bridge or enter a ruin. One may not stand in a place of similar dangers.
Ra'avad: The Yerushalmi forbids inserting a knife into an Esrog or radish for it is disgraceful to the food.
Kesef Mishneh: There is no reasoning to favor this Perush over the Rambam's. One who fears Shamayim will fulfill both of them.
Rashi (10a DH v'Ein): For Isurim, we rely on the majority, even if this is a leniency. Alternatively, regarding Isur, if we found the flask the way it was left, we are not Metamei or Posel. If water was left exposed, we forbid it, even though perhaps a person or a non-dangerous Sheretz exposed it. Even though snakes are the minority, we attribute it to them and forbid. Alternatively, even if he himself opened it and it delayed long enough for a snake to drink, we forbid, even though he found it like he left it.
Rashi (Rosh Hashanah 16b DH Kir): If one walks under a leaning wall, this arouses the question if he deserves a miracle. Through this, he is judged for his sins.
R. Bechaye (Bamidbar 16:21, brought in R. Akiva Eiger YD 116:5): Hash-m can kill and leave alive whomever He wants, even if they are together - "Yipol mi'Tzidcha Elef..." Even so, he told everyone to separate from Korach, Dasan and Aviram, lest the bad air in Dever cling to them, like we find that Lot's wife looked at Sedom (and died). Alternatively, this is because when Midas ha'Din is ruling, it does not distinguish between Tzadikim and Resha'im.
Shulchan Aruch (YD 116:5): One must be careful not to put coins in his mouth, lest there is on them saliva of a leper. One must not put his hand under his underarm, lest he touched a Metzora or poison. One must not put a loaf under his underarm, due to sweat. One must not put a cooked food or beverage under the bed, for Ru'ach Ra'ah dwells on it. One must not insert a knife into an Esrog or radish, lest one fall on the blade and die.
Ashrei ha'Ish (1:25:4) says that ha'Gaon R. Y.S. Elyashiv, Shlita, based on Tzelusa d'Avraham, does not kiss the cover of the Sefer Torah itself, due to others' saliva. Rather, he (touches his hand to it, and) kisses his hand. Sha'ar Efrayim (10:4) says that we kiss the cover itself, and so says Halichos Shlomo 12(68).
Rema: Similarly, one must beware of everything that leads to danger. Danger is more stringent that Isur. One must be more careful about Safek danger than Safek Isur. Therefore, Chachamim forbade to go in any dangerous place, e.g. under a leaning wall or alone at night. One may not drink water at night, or put his mouth to drink from falling water, for these matters are dangerous. It is forbidden to rely on a miracle or endanger oneself.
Beis Yosef (DH v'Tzarich): The Tur says that we are more stringent about Safek danger than Safek Isur. This is the conclusion in Chulin. The Rambam brought many things forbidden due to danger. One who transgresses and says 'I will endanger myself. This does not affect others', or 'I am not particular about this', we lash him mid'Rabanan.
Shach (5): One may not be secluded with a Nochri, due to danger.
Pischei Teshuvah (6): Be'er Heitev (8) says to be careful not to cut fruit trees. Besamim Rosh (334) permits if one needs its location, for the Rambam says that the primary Isur is when done destructively. Perhaps this is not destructive if one needs its location. One need not be stringent about telling a Nochri to cut it. She'alas Ya'avetz (1:76) says that if one uproots it with its roots and replants it elsewhere and it can live, surely this is permitted. The Chasam Sofer (102) said that he would not be lenient in practice. However, if one needs the place of a tree, he may not cut it if he could uproot it and replant it elsewhere. There is danger even regarding a Safek.
Kerem Shlomo (YD 368): Even the Rambam, who holds that Safek mid'Oraisa l'Chumra (we are stringent about a Torah Safek) is only mid'Rabanan, agrees that the Torah forbids Safek danger. It says "you may cut a tree only if you know that it is not a fruit tree." It is forbidden in a case of Safek because it is dangerous (Bava Kama 91b).
Sedei Chemed (Ma'arechet Samech, 74): This is a Chidush. It needs support.
Yabi'a Omer (1 YD 9): Also the Pri Megadim (Eshel Avraham 4:2) says that even the Rambam holds that Safek danger is Asur mid'Oraisa.
Note: The Pri Megadim did not explain the reason. Perhaps Sedei Chemed questioned Kerem Shlomo's source. Seemingly, there is no natural danger (Yabi'a Omer himself makes such a distinction - see below) to cut fruit trees, just we find that Hash-m punishes severely in this world for this!
Levush (116): One must flee from the city at the beginning of Dever (pestilence), not at the end. One who guards his soul will stay far away. One may not rely on a miracle or endanger his soul.
Radvaz (at the end of Avkas Rochel 213): In this matter (animals with stricken intestines) there is Isur and danger. Even Sefek-Sefeka (two doubts) does not help to be lenient.
Mishbetzos Zahav (OC 173:2): Even when there is Chezkas Isur, we do not forbid when there is a Sefek-Sefeka. According to the opinion that Sefek-Sefeka is weaker than Chazakah, it does not permit Safek danger, for we are more stringent about danger than Isur. However, according to the opinion that Sefek-Sefeka is like a majority or even stronger, we can say that it permits Safek danger. This requires investigation.
Yabi'a Omer (1 YD 9): We are stringent about Safek danger, even when there is Chezkas Heter. This is clear from the case of a bird pecking at a fig or a mouse nibbling on a watermelon. We are concerned lest there was already a hole there. Safek danger is more stringent than Safek Isur. Rashi says that even a majority does not permit Safek danger. The Pri Megadim says that according to the opinion that Sefek-Sefeka is like a majority, we are lenient about danger. This is unlike Rashi. The Shevus Yakov says that Chezkas Heter does not help for danger. Here is unlike the case in Chulin. Snake venom is a natural danger. In the days of the Gemara, when snakes were common, they were stringent even against Chezkas Heter, because danger is more stringent that Isur. Ru'ach Ra'ah is not a natural danger. It is dangerous only due to a Segulah. Perhaps we rely on Chezkas Heter to be lenient. We have no source to be stringent about this. Keren l'David (OC 1) says so. Initially I wanted to say that the reason why we are lenient about Sefek-Sefeka determines whether it helps for danger. The Pnei Yehoshua (Kesuvos 9a Tosfos DH Lo) says that according to the Rambam and Ramban, who hold that Safek mid'Oraisa l'Chumra is only mid'Rabanan, a Sefek-Sefeka is a Safek mid'Rabanan, therefore we are lenient about it. The Pri Megadim (Eshel Avraham 4:2) says that even the Rambam holds that the Torah forbids Safek danger. If so, even a Sefek-Sefeka of danger is forbidden. According to Tosfos and others who hold that mid'Oraisa we must be stringent about Safek mid'Oraisa, we must say like the Pri Chodosh, that one Safek is like an even doubt, and a Sefek-Sefeka is like a majority, therefore we are lenient. Also regarding danger, we need not be concerned for the minority. All the more so we may say so according to the Terumas ha'Deshen (129) and several others, who say that Sefek-Sefeka is better than a majority. Perhaps even the Rambam could say that Chachamim were stringent only about a single even Safek, but a Sefek-Sefeka is better than a majority. However, Avkas Rochel and Sho'el u'Meshiv (2:3:118) say that Sefek-Sefeka does not help for danger.