Avodah Zarah Daf 30 עבודה זרח דַף 30

The Gemara discusses numerous cases of גילוי – the prohibition of uncovered liquids (the concern that a snake may have drunk from it and injected its venom into it). Rabbah and Rav Yosef said: יין מזוג אין בו משום גילוי – Diluted wine is not subject to the prohibition of uncovered liquids, because snakes do not drink diluted wine. יין מבושל אין בו משום ניסוך – Cooked wine is not subject to the "נסך" prohibition of an idolator’s wine. The Gemara asks if יין מבושל is subject to גילוי, and several testimonies are related permitting it. Although an אמורא once told his attendant to dilute his wine to discourage an approaching snake, the Gemara suggests that it only risks its life for undiluted wine. The Gemara objects that a snake once put water into a barrel until the wine rose over the cloth covering and drank it (with people nearby), indicating it does risk its life for diluted wine!? The Gemara suggests that a snake only does so for wine it diluted, but not that someone else diluted, but the Gemara protests: פירוקא לסכנתא – are you giving answers regarding danger? We cannot rely on suggested answers regarding danger. Indeed, Rava rules that all יין מזוג is subject to גילוי and נסך (but יין מבושל is subject to neither).

Rebbe Yehoshua of the South said: שלשה מיני ארס הן – there are three types of snake venom: של בחור שוקע – That of a young snake sinks to the bottom of the container, being thick, של בינוני מפעפע – that of a middle-aged snake penetrates to the middle, ושל זקן צף – and that of an old snake floats on top. The Gemara objects that a Baraisa lists fish, snakes, and pigs as creatures which grow stronger with age, and answers that although it grows stronger, זיהריה קליש – its venom weakens. The relevance of a young snake’s venom sinking is taught by a Baraisa, which states that if a barrel was left uncovered, then even if nine people drank from it, apparently indicating it does not contain venom, a tenth should still not drink from it, since there may be venom at the bottom. There was such an incident in which the tenth person to drink from an uncovered barrel died, and Rebbe Yirmiyah explained: זהו שוקע – this is a case of sinking venom. The same is taught regarding a melon left exposed, with a parallel incident and explanation.

A Baraisa states: מים שנתגלו – water that became uncovered, הרי זה לא ישפכם ברשות הרבים – one should not spill it out into the public domain, where someone walking barefoot may step on it, and it may penetrate his skin. He should not sprinkle his house with it to keep the dust down, nor knead clay with it (because it may penetrate his hands). He should not give it to his or another person’s animal to drink, nor wash his face, hands, or feet with it. Others say that any body part with a סירטא – crevice should not be washed with it, which means to exclude the tops of the hands and feet, and cheekbones (which are smooth). The Gemara quotes another Baraisa which permits giving it to one’s own animal to drink, and explains this refers to שונרא – a cat, which can withstand snake venom. Still, it is prohibited to give it to someone else’s cat, since it weakens it. Although it will recover, the owner may wish to sell it in the interim, and its value will be diminished.