The melakha of Kosheir refers to binding things together by tying them, while Matir refers to separating things by undoing this connection. Unlike Tofer, which refers to joining together soft things and uniting them, and unlike Boneh, which refers to joining together hard things and uniting them, Kosheir refers to connecting things without actually joining and integrating them together as one.
As we have seen (9:2), all the melakhot that are forbidden on Shabbat have their roots in a melakha that was necessary to erect the Mishkan. This is true of Kosheir and Matir as well. It was necessary to tie the threads of the curtains that were cut during the weaving into knots. Additionally, it was necessary to tie knots in order to prepare nets for trapping snails. These snails provided tekhelet for dyeing the threads of the curtains. If a net was missing a strand, it was sometimes necessary to undo the knots from a different net and remove a strand from it (Shabbat 74b). (In y. Shabbat 15:1, Amora’im disagree whether tying the curtains of the Mishkan to the tent pegs was prohibited by Torah law.)
There are four types of knots:
1) A strong and durable knot that is not meant to ever be undone. Tying such a knot is prohibited by Torah law. Examples of this type of knot include the knots of tefilin and the knots of tzitzit. One should be careful to avoid tightening tzitzit knots on Shabbat.
2) A knot that has an element of permanence, like a knot that one plans to leave intact for a week. Tying such a knot is rabbinically prohibited. Similarly, a professional knot tied by a craftsman, even if it is meant to last less than a week, has an element of permanence, and the Sages prohibited tying it on Shabbat.
3) A temporary knot, which is meant to last for less than a week and is not a professional knot. One may tie such a knot on Shabbat.
4) Knots that are so weak that they are not even categorized as knots. Examples include a single knot and a bow knot (the type used to tie shoelaces). One may use such knots to tie things together even for an extended period of time.
The laws of untying knots are parallel to those of tying them. If tying a certain kind of knot is prohibited by Torah law, untying it is prohibited by Torah law as well; if tying it is rabbinically prohibited, so is untying it. If one may tie it, one may untie it as well. A knot that one may untie in principle but that in practice is difficult to undo, may be cut. However, one should not do so in front of an ignorant person, who may come to permit things that are prohibited (MB 317:7).
. The Mishna (Shabbat 111b) and Gemara (112a) describe three types of knots. The first type, which includes a camel driver’s knot and a sailor’s knot, is prohibited by Torah law. The second type of knot is rabbinically prohibited, and the third type is permitted. There are two positions among Rishonim regarding the definitions of these types of knots. The first position, advanced by Rashi, Rosh, Sefer Ha-Teruma, Smag, Smak, Roke’aĥ, Or Zaru’a, and others, maintains that a permanent knot is prohibited by Torah law. If it is meant to last for an intermediate amount of time, it is rabbinically prohibited; and if it is meant to last for a short period of time it is permitted. An intermediate amount of time, according to Mordechai and Tur, refers to a week or less. Kol Bo and Hagahot Maimoniyot insist that an intermediate amount of time is 24 hours, while less than that is a short period of time. A permanent knot, according to most poskim (including Shibolei Ha-leket, Yere’im, Rivash, Taz, SAH, and MB) is one that is intended to last forever. Virtually all poskim agree with this. (Rabbeinu Yeruĥam maintains that half a year is enough to be considered permanent, while Rabbeinu Peretz says that even eight days counts as permanent; see Menuĥat Ahava 3:14:4.)The second position, advanced by Rabbeinu Ĥananel, Rif, Rambam, Rivash, and SA 317:1, maintains that if a knot requires a craftsman to tie it and is permanent, it is prohibited by Torah law. If it is a craftsman’s knot but it is not permanent, or if it is permanent but can be done by a layman, it is rabbinically prohibited. If it is a layman’s knot and is impermanent, then even if one plans to leave it for an extended period of time it is permitted. This is how the second position is understood according to most Aĥaronim (Pri Megadim; Maĥatzit Ha-shekel; BHL s.v. “she-eino”). However, according to Shiltei Giborim and Tehila Le-David 317:1, if the knot is meant for an intermediate amount of time, even though it is not a craftsman’s knot, Rif and Rambam would agree that it is rabbinically forbidden.
The bottom line is that, since these are both important positions, it is proper to follow both of them even in a case of doubt about a rabbinic law. Therefore, I included both positions in the main text. However, if necessary, as long as the doubt is about a rabbinic law, one may be lenient. When there is an additional reason to be lenient, then one may be lenient even if it is not a time of need, and only those who are particularly meticulous would still be stringent.
There are two cases that are points of contention separating the two positions:
- a) A craftsman’s knot that is made to last only a short period of time (either less than 24 hours or less than a week). According to Rif and Rambam, this is prohibited rabbinically; while according to Rashi and Rosh, it is permitted. However, since we try to follow both positions, we are stringent in this case.
- b) A layman’s knot that will last for an intermediate amount of time. According to Rashi and Rosh, this is rabbinically prohibited; while according to Rif and Rambam (following the way that most understand them), it is permitted. Since in any case some maintain that up to a week is considered short term according to Rashi and Rosh, a layman’s knot meant to last less than a week can be permitted. However, if it is meant to last a week or longer it should not be permitted, as this is the opinion of most poskim. After all, according to Rashi and Rosh it is certainly forbidden, and some maintain that even according to Rif and Rambam it is forbidden (Shiltei Giborim; Tehila Le-David).
Based on the understanding of Levush 317:3, there is another leniency for knots. If a craftsman tied a layman’s knot intending for it to be temporary, but it was left for an extended period of time, it may be untied. For example, let us say that a shoemaker repairs a pair of shoes and ties them together to keep them paired until the owner comes to retrieve them, but the owner does not come for an extended period of time. Although the knot actually lasts an intermediate amount of time, according to Levush one may untie it. Taz and SAH, though, are stringent. It seems that SA 317:3 and MB ad loc. 21 would agree with Levush. This is because the temporary nature of the knot is absolutely clear. It is only because the owners did not come to reclaim the shoes that it has not yet been untied. It is not even being used to carry around the shoes. Besides, the whole disagreement between Taz and SAH on one hand and Levush on the other is relevant only to the position of Rashi and Rosh. In contrast, Rif and Rambam maintain that when a layman’s knot is made to last an intermediate amount of time, there is no prohibition of tying or untying it. The accepted ruling follows Levush, as SSK ch. 9 n. 60 states.
In practice, although the principles of Kosheir and Matir are well defined, uncertainties have arisen regarding many knots that are common nowadays. These include questions about whether certain knots should be considered craftsmen’s knots or laymen’s knots, and whether certain types of knots are considered knots at all, as explained in the next paragraph in the main text. In each case, the halakha is based on consideration of all opinions and uncertainties.