Temurah 12a-b – Losing track of a grave

In the context of teaching that an animal that had become sanctified by means of temurah (i.e. the owner of a sanctified animal attempted to switch the sanctity onto another animal so that ultimately each become sanctified) cannot cause another animal to become sanctified by means of temurah – ein temurah oseh temurah – the Mishnah on today’s daf(=page) lists a number of similar laws. One of them is the rule that ein beit ha-peras osin beit ha-peras – an area with a grave cannot create an area with a grave.

The law of a beit ha-peras teaches that a field that has doubtful status regarding ritual defilement of a dead body must be treated stringently. When we know that there was a grave in a given field, when that field is plowed the doubtful ritual status may be created either because we fear that the plowing may have dislodged bones that now may be spread throughout the field or that the grave was “lost” and we cannot be certain where the body is buried.

With regard to the source of this expression, Rashi and Tosafot agree that the word peras means “broken” and that we fear that the original grave and its contents have been broken by the plowing. According to the Rambam, the term perasmeans “spread out,” since we treat the field as if the ritual defilement is spread across the entire field. Others suggest that the source may be Greek expressions meaning “courtyard” or a place that cannot be crossed.