On today’s daf, the rabbis are engaged in a head-spinning conversation about situations that might invalidate an eruv techumin, the type of eruv that extends the distance one can travel on Shabbat and which has been a topic of conversation for many pages now — and will be for several more. So buckle up.
On yesterday’s daf, the rabbis began discussing a situation in which the food that constitutes an eruv techumin is locked in a cupboard and the key has been lost. The mishnah on the previous daf declared that in such a case, the eruv is still valid. But the mishnah also recorded a dissenting opinion, from Rabbi Eliezer, that invalidated such an eruv.
On our daf, the Gemara daf drills down on this ruling, trying to figure out the specific situation referred to in the mishnah. Eventually, the Gemara determines that the case is one in which the cupboard holding the eruv is closed with a lock that is tied with a leather strap, requiring a knife to cut the strap since the key cannot be found. The question then becomes whether the knife can be used on Shabbat.
The Gemara concludes that the permissive opinion in the mishnah is based on the view of Rabbi Yosei, who said: “All utensils may be moved on Shabbat, except for a large saw and the blade of a plow.” Saws and plows are items used for tasks that are forbidden on Shabbat and therefore they can’t be moved either. But a knife can be used on Shabbat. So the mishnah determines that a knife, being a tool that can be used on Shabbat, can also be taken and used to cut the strap to access the eruv.
Rabbi Eliezer’s restrictive opinion, on the other hand, is based on the view of Rabbi Neḥemya, who said: “Even a cloak, and even a spoon, which are certainly used only for activities permitted on Shabbat, may be moved on Shabbat only for the purpose of their ordinary use.”
According to this view, while a cloak and a spoon are both items that can be used on Shabbat, they may only be moved in the event that they are needed for their regular purpose. The same principle, according to Rabbi Eliezer, would apply to a knife: It can be moved to cut food, but not for any other purpose. Therefore, you cannot carry the knife to the cupboard. And even if you could, using it on Shabbat for a purpose that is not cutting food is also forbidden. Therefore, the eruv locked in the cupboard is invalid.
This is, of course, a highly specific situation. It’s not likely that most of us are going to find ourselves in a circumstance where our eruv is locked in a cupboard tied with a strap and our key is lost. But it’s important to remember that the central idea of Shabbat is refraining from normal creative weekday work. By restricting ourselves to using tools that have a permissible use on Shabbat, and only using tools for their normal purpose, we keep ourselves from improperly using the tools to be creative. Being mindful about how we use tools, which are quite literally vehicles for creativity, ensures that we truly embrace the atmosphere of Shabbat.