The Mishnah in Masechet Shabbat (73a) lists the thirty-nine forms of forbidden work on Shabbat. The Mishnah includes “tying and untying” among them. One who ties or unties a knot on Shabbat is tantamount to having kindled a fire or planted wheat on Shabbat.
There are several detailed laws regarding this prohibition, for not all knots are forbidden to tie or untie on Shabbat as we shall now begin to explain.
The Laws of Tying and Untying are Contingent Upon One Another
We must first explain that the laws of tying and untying a knot are dependent on one another. This means that any kind of knot which is forbidden to tie on Shabbat is forbidden to untie on Shabbat as well. Likewise, any kind of knot which is permitted to be tied on Shabbat may be untied as well. The Rambam (Chapter 10 of Hilchot Shabbat, Halacha 7) and Maran Ha’Shulchan Aruch (Chapter 317, Section 1) rule accordingly (see Chazon Ovadia-Shabbat, Part 5, page 47).
Knots Forbidden by Torah and Rabbinic Law
Some knots are forbidden to be tied by Torah law on Shabbat. Others are permitted by Torah law, but forbidden by rabbinic law as an additional “fence” (precaution) to the Torah’s laws.
Knots Forbidden by Torah Law-Permanent and Professional Knots
If one ties a “permanent” knot on Shabbat, i.e. a knot that is not meant to be undone within the next day or the next week (as we shall soon explain), if this knot is “professionally done”, i.e. not all individuals know how to tie such a knot, for it takes certain knowledge and skill to tie such a knot, one is liable by Torah law as a result of the knot he has tied, similar to any other form of Shabbat desecration.
An example of a knot forbidden on Shabbat by Torah law is a “Camel-Driver’s Knot.” This entailed making a hole in the saddle or through the camel’s nose through which leather straps would be passed and tied strongly such that it would never become untied. This kind of knot is considered both “permanent” and “professional.” For this reason, one who ties such a knot on Shabbat is liable by Torah law.
Similarly, a “sailor’s knot,” i.e. when rope is inserted in a hole located in the front of a ship and tied very tightly so that it is firm enough to tie another rope to it to hold the boat in place in the dock, is considered a “permanent” and “professional” knot and is forbidden to be tied on Shabbat by Torah law. In the next Halacha we shall discuss several knots which are permitted by Torah law to be tied on Shabbat but forbidden by a rabbinic enactment.
