While the thirteenth perek (=chapter) of Masechet Zevahim dealt with the prohibition of performing the sacrificial service outside of the Temple, the fourteenth perek, which began on yesterday’s daf (=page) deals with various situations where an animal is sanctified, yet is not brought as a normal sacrifice. In cases like burning a parah adumah – a red heifer (see Bamidbar, Chapter19) – the animal is not a sacrifice, yet there are specific laws that must be followed in order to prepare it for use in the Temple.
The Mishnah (112a) teaches that if the parah adumah was slaughtered and burned outside of the special pit that was prepared for that purpose on the Mount of Olives, nevertheless the person who did that would not be held liable for performing the Temple service outside of the appointed place. The Torah clearly limits this prohibition to animals that are to be brought as sacrifices in the Temple (see Vayikra 17:3-4), and the parah adumah does not fall into that category.
The Gemara on today’s daf asks what is special about the place that was set aside for preparing the parah adumah. Although the Mishnah in Masechet Parah (4:2) teaches that there is a specific place that it should be prepared, the Torah makes no mention of such a requirement. Resh Lakish taught that this was a special place that had been certified as containing nothing that might ritually defile the parah adumah. Rabbi Yohanan objects to this teaching, arguing that all the land of Israel has been checked and found to be pure of such defilement.
The Gemara explains this disagreement as being based on how these Sages viewed the destruction of the Flood. According to Rabbi Yohanan, the land of Israel was not affected by the flood, so there is no fear that there are bones buried in unmarked and unknown graves. Resh Lakish believes that the Flood reached the land of Israel, as well, so only places that had been scrupulously checked could be certified as pure.