To complete an eruv, one must place a quantity of food within its confines. On today’s daf, the Gemara explores the circumstances under which one can delegate that task to others.
The mishnah teaches:
If one sends his eruv in the hands of a deaf-mute, an imbecile, or a minor, all of whom are regarded as legally incompetent, or in the hands of one who does not accept the principle of eruv, it is not a valid eruv. But if one told another person to receive it from him at a specific location and set it down in that spot, it is a valid eruv.
The mishnah identifies four categories of people upon whom one cannot depend to establish an eruv. The first category is the deaf-mute. In our day, such people are able to function in society with proper support, but during the time of the Talmud, communication with those who were deaf and mute was limited. As a result, the rabbis prohibited them from acting as agents because one could not be certain that they fully understood what they were being assigned to do. For similar reasons, the rabbis excluded those with diminished mental capacities and children.
The final category refers to Jews who follow biblical law, but not the rabbinic rules derived from them. As the concept of eruv is a rabbinic construction, Jews who did not accept rabbinic authority could not be trusted to properly establish an eruv.
In the final part of the mishnah, we learn that while people in these categories may not establish an eruv, they can be assigned the task of delivering food to a more trustworthy agent who would then complete the activation.
But wait, the Gemara asks, if we can’t trust certain people to construct an eruv properly, why can we trust them to deliver the food for an eruv?
The Gemara provides two answers. The first is that the mishnah was referring to a case where a person watches the food being delivered. In this view, you can send food by unreliable messenger only if you can see the delivery take place. The second answer is that there is a legal presumption that an agent fulfills their mission. As a general rule, we do not have to witness the delivery personally to be confident that it took place.
Why do the rabbis differentiate between the act of delivering the food and that of placing it to form the eruv? The former task in and of itself has no legal or ritual implications, so the rabbis allow those who may not fully understand what they are doing to complete it. But the act of placing the food to make an eruv operational does have significance in Jewish law, so it can only be delegated to someone the rabbis identify as a competent agent.
The rabbis push this point even further by referencing the teaching from which this distinction is derived:
If one gave food for an eruv to a trained elephant, and it brought it to the place where one wanted it to be deposited, or if one gave it to a monkey and it brought it to the proper location, it is not a valid eruv. But if one told another person to receive it from the animal, it is a valid eruv.
While it may be shocking to read that the rabbis placed deaf-mutes, imbeciles, and Jews who reject rabbinic authority in the same category as trained animals, the analogy provides some insight into how the rabbis thought about agency. When it comes to tasks that have legal or ritual significance, only those with the capacity to comprehend what they are doing are deemed trustworthy. While the rabbis were not always as sensitive and inclusive as we might wish them to be, this requirement does make sense.