For many pages now, the Gemara has been discussing issues relating to the construction of an eruv in a place where some people don’t participate in it, either because they forgot or because they’re not Jewish or because they don’t accept the idea of eruv in the first place. As we’ve seen, an eruv can be established in such a case only if the non-participants give up their ownership rights.
It makes sense that this topic is consuming significant ink. Then, as now, observant Jews lived among non-Jews and Jews who didn’t observe, and the rabbis had to find ways to navigate that reality. One of those ways, as we saw back on Eruvin 61, is by means of a sechirat reshut — essentially a property rental, which is how modern eruvim are constructed in large cities. Another way (generally for smaller settings) is by having the non-participants in the eruv renounce their rights to the shared space for the duration of Shabbat.
On today’s daf, the Gemara considers a rather obscure circumstance related to this practice: What happens if a non-participant dies on Shabbat?
Rava raised a dilemma before Rav Nahman: With regard to an heir, what is the halakhah regarding whether he may renounce rights in a courtyard? If a person who had forgotten to establish an eruv died on Shabbat, may his heir renounce his rights in his stead?
Rava wants to know what happens if someone who forgot to establish an eruv with their neighbors dies on Shabbat. May the person’s heir renounce the deceased’s rights in their stead and enable the eruv to take effect?
The Gemara suggests two possible answers. One is that a person can only renounce their rights on Shabbat if they had the option of renouncing their rights before Shabbat. Since the heir did not have that right on Friday, as his father was then still alive, the heir can’t exercise that right on Saturday. The second possibility is that the heir is, in the Talmud’s inimitable language, “like his father’s foot.” That is, the heir is a stand-in for the father in all respects. If the father could have renounced his rights on Shabbat, so can the son.
In trying to puzzle their way through this, the rabbis bring down this teaching:
This is the principle: Anything that is permitted for part of Shabbat is permitted for all of Shabbat, and anything that is prohibited for part of Shabbat is prohibited for all of Shabbat, apart from one who renounces his rights.
This teaching has some fairly wide-ranging implications. Essentially, it tells us that, with one notable (and highly relevant for our case) exception, the status of things forbidden or permitted on Shabbat is static. If an eruv was established on Friday to permit carrying on Shabbat in a given area, the eruv remains in effect even if the posts demarcating it blow over in a storm. Similarly, if non-Jews decide to build a wall enclosing an alleyway on Saturday morning, it would still be forbidden to carry within it because no such enclosure was present on Friday afternoon.
This is a mighty useful principle. But it’s equally notable the one exception the rabbis have carved out — the renunciation of property rights. So vital was it to have an eruv available on Shabbat that this is the one area of Shabbat prohibitions that can be changed, even on Shabbat itself.
And that business about the heir? The Gemara hinges its understanding, naturally, on a close reading of the teaching: “apart from one who renounces his rights.” The “one” who renounces must mean the original owner — not the heir.