Many times, for those who have two double knots with eight strings in each knot (i.e. not following the opinion of the Rambam), the knot starts to come loose often, sometimes even several times a day. If it is not tightened, occasionally it will completely come out by the end of the day.

My question is, if someone notices on Shabbos that their tzitzis knot is coming loose, and is slipping down the strings, can they slide it up closer to the top, without tightening it, so that it won't come completely undone and begin to unravel further?

  • This ehow explains how to tie tzitzis. At the end it says, "Tips & Warnings Wet all of the knots with boiling water then let them air dry. This will make the knots dry tighter and stronger to prevent unwinding." The threads shrink as they dry and this is what tightens the knots. I am unsure as to whether boiling water is essential or lower temperatures are also effective. Commented Aug 12, 2014 at 20:19
  • 1
    For techniques that can be implemented before Shabbat to prevent this problem from cropping up, see this Q&A: judaism.stackexchange.com/questions/90385/…
    – Isaac Moses
    Commented Mar 14, 2018 at 16:35

2 Answers 2


The book The 39 Avoth Melacha of Shabbath* on Page 32 has an illustration that specifically forbids this (as Rabbinic, IIRC a Torah prohibition).

Image from book

It sources the statement to Kitzur Hilchos Shabbos 25, 2 and Shmiras Shabbos Kehilchasa 15, 50.

  • I think the illustration is of a knot about to be tightened. The Shmiras Shabbos reference is referring to tightening a knot, not to just sliding it closer without tightening it. Commented Nov 5, 2014 at 21:19

If the knot is high up to the top and if it is about to be undone you can bring down lower but do not tighten it. Shulchan aruch harav hilchos tzizis

  • 4
    Can you give edition, chapter and paragraph numbers?
    – Double AA
    Commented Aug 13, 2014 at 0:04
  • i will try to find Commented Aug 13, 2014 at 0:21
  • @DovidBenizri any luck finding this? Commented Nov 5, 2014 at 21:15

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