The Mishna on today’s daf teaches that if a non-Jew performs sheḥita – ritual slaughter – on an animal it is not kosher.
Rabbi Ḥiyya the son of Rabbi Abba quotes Rabbi Yoḥanan as teaching that the Mishna should be understood as forbidding eating the meat of an animal slaughtered by a non-Jew, but permitting its use for other purposes, inasmuch as we do not assume that the non-Jew had intentions to slaughter the animal for purposes of idolatry. This stands in contrast with slaughter performed by a min – a Jewish heretic – who we assume would have idolatrous intentions. This view is supported by a baraita that taught:
Ritual slaughter performed by a min is regarded as intended for idolatry, his bread as the bread of Kutim, his wine as wine used for idolatrous purposes, his scrolls of the Law as books of sorcerers, his fruit as tevel (untithed).
We learned above (daf 3) that Kutim were people who were exiled to the Land of Israel by the kings of Assyria who were interested in populating the land after they had removed the Israelite people from it. According to Sefer Melakhim (see II, chapter 17), these nations converted to Judaism because of their fear of lions that had begun attacking them (from which derives the term gerei arayot – “lion converts”), but they continued worshiping their gods at the same time. By forbidding their bread, the Sages were even more stringent regarding Kutim than ordinary non-Jews, whose bread is permitted under certain circumstances (e.g. when Jewish baked bread is not readily available, see Avoda Zara daf 35b). In contrast, bread baked by Kutim was forbidden as if it were pork (see the Mishna in Massekhet Shevi’it 8:10).
The Ramban explains that the Rabbinic enactment forbidding bread baked by non-Jews was established in order to discourage close social interaction between Jews and non-Jews, which the Sages feared would lead to intermarriage. Since the Kutim kept some Jewish laws and traditions, there was a greater concern that such relationships might develop, which necessitated more stringent rules against it. Others argue that this enactment predated the ruling that Kutim should not be viewed as members of the Jewish community (see above, daf 6a), and that it stemmed from the fact that the community of Kutim worked to undermine the rebuilding of the Second Temple during Ezra’s time.