Why can’t one wash their hands with hot water on Shabbath? Is it Biblical or Rabbinical that we not do so?

  • When was the water heated?
    – shmosel
    Commented May 6, 2023 at 0:20
  • @shmosel I’m referring to water from the faucet. Commented May 6, 2023 at 9:28
  • 1
    Because of not wanting to heat cold water with hot water in the faucet which is a Biblical prohibition
    – mbloch
    Commented May 6, 2023 at 17:28
  • @mbloch You are referring to a prohibition on opening a modern hot water tap. Washing hands itself in hot water is seemingly only a rabbinic prohibition, if that.
    – Double AA
    Commented May 7, 2023 at 1:25
  • @DoubleAA you are right, and indeed the OP did as well (as clarified in his comment)
    – mbloch
    Commented May 7, 2023 at 3:18

1 Answer 1


According to Rabbi Naftahli Silberberg

When turning on the hot water you are automatically letting new water flow into the water boiler, where they are cooked. Cooking is one of the thirty-nine creative acts that are forbidden on Shabbat. You could use the water from a percolator that was on since before Shabbat, or a samovar that's on the fire since Friday, to rinse hands or dishes.

Not all authorities agree about this, of course. As for Biblical vs. Rabbinical, it's not specifically mentioned in the Bible, since modern plumbing wasn't invented. But cooking and kindling fires (flame from a gas heater?) are indeed prohibited.

“This is what the Lord has commanded: ‘Tomorrow is a day of solemn rest, a holy Sabbath to the Lord; bake what you will bake and boil what you will boil, and all that is left over lay aside to be kept till the morning.’” (Ex. 16:23)

So technically, since modern plumbing isn't addressed in the Torah, it is Rabbinical rather then Biblical. But if you accept the idea of Oral Torah, it is a distinction without a difference.

  • Todah for the response. Commented May 6, 2023 at 19:12
  • 2
    @Dan your bring a good source, but this is not how d'oraytas and derabannans work Commented May 6, 2023 at 20:59
  • Like I said, not all authorities agree. Commented May 7, 2023 at 2:40

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