Ask the Rov: May I drink water left overnight in an urn?
By Rabbi Chaim Hillel Raskin – Rov of Anash in Petach Tikvah
Chazal cautioned against drinking water left uncovered and unsupervised — even for a very short time — due to the concern that a snake or other poisonous creature may have drank from it and left dangerous venom inside.1 The concern applies also to wine, milk, and honey, but not other liquids, such as oil or fruit juice. Poskim also exclude water that has undergone a change, like tea, coffee, soup, or even cooked wine.2
Shulchan Aruch rules that when poisonos snakes are no longer amongst us in more recent times, one needn’t be concerned about uncovered liquids (giluy).3 Yet, later poskim write that in locations where snakes are even somewhat found, one should be careful.4
The Alter Rebbe in his discussion of dangerous activities in Hilchos Shmiras Haguf V’hanefesh omits mention of this issue, and in Hilchos Kiddush mentions that we aren’t careful about giluy because poisonous snakes aren’t common among us.5 It follows that in places where snakes are actively found, one should be concerned for this halacha.
The Alter Rebbe writes that wine left uncovered shouldn’t be used for kiddush specifically because such wine is unfit for nobility. If it was uncovered for only a short amount of time, one may use it when other wine isn’t available provided the taste or smell didn’t change from being left open.6
A separate issue applies to liquid with water in it — and possibly plain water — that is left overnight in a metal utensil, as it becomes infected with a ruach raah (evil spirit).7 If followed, this would disqualify soda cans, canned foods with liquid, electric urns, cholent in a metal pot, and the like.
Although some chassidim are careful about this (and use a glass urn for Shabbos),8 the widespread custom is not to be concerned. Some explain that ruach raah is less powerful nowadays (just as we no longer avoid zugos, pairs).
The Rebbe offers various justifications for the common custom, primarily that when the public becomes accustomed to performing a dangerous activity, Chazal state, “Hashem protects the simple.” Moreover, when the danger is spiritual in nature, it is only powerful when people are afraid of it. When people are no longer careful, the danger eventually subsides.9
Additionally, a vessel that is attached — or possibly plugged in — to the ground loses its status as a “vessel.”10 Some suggest that sealed cans are not yet considered vessels.11 There may also be additional grounds for leniency with Shabbos food, as Chazal say that “one who is involved in a mitzva will know no harm.”12
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From The Weekly Farbrengen by Merkaz Anash