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The Shabbos Weekly
Halachos Series on Hilchos Shabbos

shabbos candles

Published by
Pirchei Shoshanim

A Project of
The Shema Yisrael Torah Network

Based on the Shiurim Given by

Rabbi Dovid
Ostroff, shlita

developed from the Chabura of the
Pirchei Shoshanim Shulchan Aruch Learning Project

These Halachos were shown by Rabbi Ostroff to
HaGaon HaRav Moshe Sternbuch, shlita


Questions for the Week of Parshas Vayeishev


I heard that one is forbidden to tie a sailor’s knot on Shabbos, but are not all knots forbidden?

In order to answer your question we need to lay down the foundation of this sugya. The pertaining Mishna and gemora can be found in Shabbos 111b-112a. We find that the major Rishonim differ over the understanding of the sugya and hence the ramifications greatly vary.

The Halacha subdivides the tying of knots on Shabbos into three categories: 1) Knots that are Biblically prohibited to tie, 2) Knots that are Rabbinically prohibited to tie and 3) Knots that are permitted to tie.

Ossur mid’oraisso: the gemora says – ???????? (bid’ushkepi). Rashi explains that the leather worker would insert a strap into the shoe and tie it permanently into place. Since this knot is a permanent one, it is ossur mid’oraisso.

Ossur mid’rabanan: the gemora says bid’rabanan (the student’s shoes). Rashi explains that the students would tie their shoe straps loosely to their legs enabling the shoes’ removal without having to untie the knots. Nevertheless they were not permanent knots, because when walking in mud they would untie the knots and fasten the straps tightly to their legs so that the shoe would not stick to the mud and come off.

Permitted: ??? ????? (B’nei Mechoza). Rashi explains that the people of Mechoza were meticulous with their clothing and would tie the straps tight to the point that they could not be slipped off the leg. Therefore it was not a permanent knot since they would have to fasten and unfasten the shoe straps to their legs on a daily basis.

The Rif and the Rambam add another factor – craftsmanship. They see in the sugya that for a knot to be Biblically prohibited it must be the type tied by craftsmen. The underlying feature of such a knot is its strength. [1]

So where does the sailor knot come in?

The sailor knot is a craftsman’s knot par excellence and would definitely contribute towards a perpetrator being guilty of a Biblical transgression. However time is a factor as well, as we will see.

The other factor is time and according to Rashi and the Rosh it is the only factor.

A knot tied forever – kayama – is ossur mid’oraisso.

Longer than a week or 24 hours (two opinions) is ossur mid’rabanan.

Less than a week or 24 hours (the respective opinions) is permitted.

The synopsis is as follows:



Semi permanent

< 24 hours

< a week

Craftsman’s knot

Biblical according to all

Rif  and Rambam  – Rabbinical


Rif  and Rambam  – Rabbinical

Rashi Rosh – permitted

Layman’s knot

Rif  and Rambam  – rabbinical

Rashi Rosh – Biblical

Rif  and Rambam  machlokes [2]

Rashi Rosh – Rabbinical



There are two opinions as to the permitted time factor and L’chatchila one should not tie even a simple knot on Shabbos if he intends untying it after 24 hours.

Which of the above opinions is the halacha?

The Shulchan Aruch (Mechaber) rules according to the Rif and the Rambam and The Rama rules according to Rashi and The Rosh, at least l’chumra. Accordingly one may only tie a simple knot within the permitted time bracket.

Are most knots permitted because after all most knots are not craftsmen’s knots?

Things are not so simple. The poskim hold that a strong double knot is classed as a craftsman’s knot due its sturdiness and strength; hence one may not tie a double knot even for less than 24 hours.

What about a double knot tied in a woman’s kerchief or the knot in the handkerchief tied around one’s neck, are they also forbidden?

Since the main feature of a craftsman’s knot is its strength and these particular knots are not tied sturdily, one is permitted to loosely tie them. [3] This would seemingly not apply to tying shoelaces in a double knot owing to the fact that they are fastened tightly.

[1] Shiltei Giborim and other Achronim.

[2] There is a machlokes amongst the poskim as to when neither of the Biblical factors are present whether it is ossur mid’rabanan or permitted.

[3] Zachor VeShamor, Hilchos ????, pp 7-8.

Food For Thought

May I tie a knot at the end of my tzizis, after all it is not a double knot?

If one must tie a knot on Shabbos, either for the sake of a mitzvah or for safety reasons, is he permitted to do so?

If the answer to the above is yes is there a restriction as to which type he may tie and which knot not?

Answers coming next week.

Vort on the Parsha

The possuk tells us that the Yosef’s brothers threw him into an empty pit and Chazal relate that the pit was lined with snakes and scorpions. This seems to be a contradiction to what the brothers wanted to do, after all they did not wish to kill him, but throwing one into a pit with snakes and scorpions does not really offer much hope of a grand life.

The Vilna Gaon explains the juxtaposition of two gemoras in Shabbos 21b. The first gemora says that a chanuka light placed aboves 20 amos is possul because one does not normally look so high. The subsequent gemora is the above-mentioned Chazal – the pit was lined with snakes and scorpions. The Ga’on says that the pit was 20 amos deep (based on another gemora which says that ‘throwing’ refers to the distance of 20 amos) and since the pit was 20 amos deep and one does not naturally see further than 20 amos, [1] they did not see the snakes and scorpions!!

[1] Obviously one sees much further but into a dark pit one does not naturally see the unexpected.

For a printed version, click here.


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Note:  The purpose of this series is intended solely for the clarification of the topics discussed and not to render halachic decisions. It is intended to heighten everyone's awareness of important practical questions which do arise on this topic.  One must consult with a proper halachic authority in order to receive p'sak.