As we learned on yesterday’s daf (=page), if a non-Jew owned an animal, even if the firstborn was acquired by a Jewish person, it would not be subject to the laws of bekhor. On today’s daf we find a discussion about a situation where the Jew and the non-Jew were partners in the animal. Rabbi Yehudah rules that if a Jew and a non-Jew were partners in the firstborn, the Jew is obligated to pay half of the value of the firstborn to a kohen. The Sages disagree, arguing that such an animal is entirely free from the laws of the firstborn.
According to the discussion in our Gemara, even if the non-Jew owns only a small part of the animal – Rav Huna‘s example is the animal’s ear – the obligation in the mitzvah of bekhor does not apply.
In the context of this discussion, the Gemara relates the following story:
There was a woman proselyte whose brothersgave her animals to fatten. She came before Rava to ascertain her obligation in the laws of the firstborn with regard to these animals.Rava said to her: “There is no authority that pays any attention to the ruling of Rabbi Yehudah who said: The partnership of a heathen in an animal is subject to the law of the firstling.”
Conversion to Judaism was a relatively infrequent occurrence in Babylonia, and it appears that the Persian government looked askance at people who were interested in converting. Nevertheless, during the reign of Shevor Malka —Shahpuhr — which was during Rava’s time, we find a number of conversions that took place, most of which — like the story related in our Gemara — took place in the city of Mehoza, Rava’s hometown. It is possible that this phenomenon is related to the close ties that existed between the king, Shevor Malka, and the Jewish community and its leaders in Babylonia.