OPINIONS: Rebbi Yehudah and the Rabanan argue about whether one may place an Eruv on a gravestone. Rebbi Yehudah maintains that since a person does not intend for his Eruv to remain on the gravestone throughout Shabbos, his food will not be protected from predators. Therefore, he may put the Eruv there because he will not derive benefit from the gravestone. The Rabanan maintain that a person does intend to use the gravestone to protect the food of the Eruv for the entire Shabbos. Therefore, he may not place the Eruv there, because he will benefit from the gravestone. What is the Halachah?

(a) The SHULCHAN ARUCH (OC 409:1) rules like the Rabanan, the majority opinion, who say that one may not use a gravestone for an Eruv, because one thereby derives benefit from the gravestone.

(b) However, the BI'UR HALACHAH cites the MAHARAM, ROSH, TUR, and RASHBA who conclude that the Halachah follows the view of Rebbi Yehudah, because of the principle that "the Halachah follows the lenient opinion in laws of Eruv, even when it is the opinion of a minority" (Eruvin 46a). Accordingly, in extenuating circumstances, one may rely on an Eruv which was placed on a grave.

The Bi'ur Halachah points out that the allowance to rely on an Eruv placed on a gravestone only applies to a Yisrael. A Kohen may not rely on such an Eruv because it is impossible for him to get to the gravestone to eat the food. (Even if he is carried into the graveyard in an enclosed box ("Shidah, Teivah, or Migdal"), we rule that "Ohel Zaruk Lav Shmei Ohel" and the box does not serve to protect him from the Tum'ah of the graveyard.)

(According to Rashi, when the grave is not in a graveyard but is an isolated grave in a field, the Eruv is valid even for a Kohen, because he may approach the grave and grasp the food at a point which protrudes from the gravestone.)