As we learned in the Mishna (daf 15), the second perek of Massekhet Zevaḥim deals with situations where there is some problem with the person who brings the sacrifice. One of the examples that appears in the Mishna is the case of a tameh – someone who is ritually defiled – who sacrifices. The Gemara on today’s daf brings Ziknei Darom– the Southern Elders – who limit this to cases where the ritual defilement stems from a relatively simple tumah, like someone who came into contact with a dead sheretz – an animal whose carcass transmits ritual defilement. If, however, the kohen was more seriously defiled, e.g. he had come into contact with a dead person, then his sacrifice would be accepted. The argument of Ziknei Darom is that since we know that serious defilement is set aside when the entire community is tameh, even in situations where we have an individual situation of defilement, the sacrifice will be accepted.
The source for serious defilement being set aside when the entire community is tameh is the passage in Sefer Bamidbar (9:2) that teaches that the Passover sacrifice was brought be-mo’ado – in its proper time. This is understood to teach that when a communal sacrifice must be brought, the ritual purity of the community will not be an impediment to bringing the korban. This stands in contrast to the laws of the individual who has become ritually defiled because of contact with a dead person, whose source is the continuation of Sefer Bamidbar (9:9), who will not be permitted to bring the sacrifice – although in the case of korban Pesaḥ he will be offered a “make-up date” the following month.
The term Ziknei Darom refers to the Sages who lived in Judea – in the southern part of Israel – during the times of the amora’im. During that period, most of the Jewish community in Israel lived in the Galilee, which contained the centers of Torah study. Although the communities in the South were decimated by war, nevertheless there remained Sages who carried on the traditions of that community.