The Gemara in tractate Avodah Zarah explores the laws concerning liquids that may have been used for idolatry or compromised by physical danger. Rav Ashi begins by clarifying a ruling regarding vinegar belonging to a gentile. If the liquid began as wine and subsequently turned into vinegar, it remains forbidden for use or benefit. The logic is straightforward: if the liquid was forbidden while it was wine—due to the concern that it was used for an idolatrous libation—that prohibition does not vanish simply because the wine’s physical state has changed into vinegar.
However, Rav Ashi notes an important distinction when a Jew gives his own vinegar to a gentile to guard. In such a case, the Jew does not need to apply a double seal to the container; a single seal is sufficient. This is because we are not concerned that the gentile will use the vinegar for an offering, as vinegar is not used for libations on an altar. Furthermore, we do not fear that the gentile will swap the Jew’s vinegar for his own, because the effort required to forge a seal is not worth the trouble for a product as common as vinegar.
A similar logic applies to cooked wine. Rav Ila teaches that if a gentile possesses cooked wine that began as regular wine, it is forbidden. If the wine was potentially used for an idolatrous libation before it was cooked, the subsequent cooking does not remove the forbidden status. Yet, if a Jew entrusts his own cooked wine to a gentile, a single seal is enough. Gentiles consider cooked wine to be an inferior product and do not use it for their religious rites. Therefore, the concern of libation is removed, and a single seal provides enough security against the gentile swapping the wine.
The Gemara then discusses a medicinal cooling drink known as aluntit, which consists of old wine, clear water, and balsam. If this drink is produced by gentiles, it is forbidden because of the wine it contains. However, if the drink was originally made by a Jew and then came into the possession of a gentile, it is permitted. Since the finished mixture is not used for idolatrous libations, we do not fear that the gentile would use it for such a purpose once it has already been prepared.
The conversation shifts to the danger of uncovered liquids, which may contain snake venom. Rabbah and Rav Yosef initially suggest that diluted wine is not subject to this concern because snakes are particular and do not drink watery wine. They also state that cooked wine is exempt from the laws of libation. The Gemara seeks to clarify if cooked wine is also exempt from the danger of being uncovered. Rabbi Yaakov bar Idi and Rabbi Yannai bar Yishmael provide testimony that snakes do not drink cooked wine, meaning it remains safe even if left uncovered. Rabbi Yishmael ben Zirud confirms this in the name of Resh Lakish and Rabbi Chiya, even signaling with his own life that the ruling is reliable.
Practical examples of these laws are found in the lives of the sages. When Shmuel sat with a gentile stargazer named Ablat, they were served cooked wine. When Ablat hesitated to touch it, Shmuel assured him that cooked wine is not subject to the prohibitions of gentile wine. Similarly, the servants of Rabbi Chiya and Rav Adda bar Chama were told that cooked or diluted wine left uncovered remained permissible. However, Rav Papa qualifies the rule for diluted wine, noting that snakes will only avoid it if it is significantly watered down. If the dilution is minimal, the danger remains.
The Gemara questions whether snakes truly avoid diluted wine, citing a story involving Rabbah bar Rav Huna on a boat. When a snake swam toward his wine, he added a drop of water, and the snake turned away. This suggests that while a snake might risk its life for pure wine, it will not do so for a diluted mixture. Conversely, stories involving Rabbi Yannai and Bar Hadaya show that in a safe environment, such as a house, a snake might even go to great lengths to drink diluted wine, even adding water to a jug to make the wine float to the top. Because of these conflicting observations regarding safety, Rava rules stringently: diluted wine must be treated as a danger if left uncovered and is also subject to the prohibitions of gentile wine. Cooked wine, however, remains exempt from both concerns.
Regarding the protection of liquids, the Gemara clarifies that sleeping next to a vessel does not protect it. While a snake might be deterred by someone awake during the day, it does not fear a person in a deep sleep at night. There is also a dispute regarding which households can be trusted. Rav would drink from the home of a Jewish widow, assuming she maintained the careful habits of her late husband, but he would not drink from a gentile. Shmuel disagreed, fearing a widow lacked the oversight of a husband to remain careful, while trusting that a gentile might cover liquids simply for the sake of cleanliness.
Further exemptions are made for specific types of wine that snakes find unpalatable, such as those that are excessively sharp, bitter, or over-sweetened by the sun. Rav Chama suggests that even certain high-quality spiced wines are ignored by snakes. Rava adds that wine turning into vinegar is only a concern for the first three days; after that, it is too sour for a snake and unfit for an altar. Other exceptions include bubbling new wine, which scares snakes with its noise, and liquids that are steadily and noisily dripping. In a display of trust in Divine protection, Rav Chiya bar Ashi cites Shmuel and Rabbi Eliezer to teach that one may even eat plucked figs or grapes at night without fearing that a snake poisoned the open stem, as the Creator protects the simple.
Finally, Rav Safra, in the name of Rabbi Yehoshua Deromaya, describes the nature of snake venom. A young snake’s venom sinks, a middle-aged snake’s venom permeates the middle, and an old snake’s venom floats. While a snake grows stronger with age, its venom becomes lighter. This distinction carries a heavy practical warning: Rabbi Yirmiya notes that one should never drink the end of a barrel that was left uncovered, even if nine people drank from it and survived. If the venom came from a young snake, it would have settled at the very bottom, waiting for the tenth person. This reality is reinforced by tragic accounts of people who died after eating the final portion of a melon that had been left exposed.