The first Mishna in Massekhet Bava Metzia (2a) discusses the case of shenayim ohazin be-talit – two claimants holding one end of a cloak, each claiming that it belongs to him. Our Gemara asks how we should treat the case if one of them declares makdish (declares it sanctified to the Temple) what he claims belongs to him.
To examine this question, our Gemara tells the story of two people who each claimed ownership of a bathhouse. One of the claimants announced that he was being makdish the bathhouse, a statement that led Rav Hanania, Rav Osha’aya and the rest of the Sages to refrain from entering it. This decision was not based on a definitive ruling, but was made because the Sages were unsure about the status of the bathhouse at this point. Rav Osha’aya instructed Rabbah to pose the question to Rav Hisda in Kafri in order to receive a ruling on the matter. Upon reaching Sura, he met Rav Hamnuna who suggested that the question could be compared to a case of safek bekhor (a situation where it is not clear whether an animal was firstborn and belonged to the kohen or not), where the animal cannot be used for any ordinary purposes. Rabbah rejected the comparison, arguing that we must distinguish between a safek bekhor whose holiness is integral – it comes automatically when it is born – and our case where any holiness is imparted on it from its owner’s declaration.
The city of Kafri was situated in Bavel, about 20 kilometers south of Sura. It apparently contained an ancient Jewish community, since it was the seat of the Resh Galuta – the head of the Diaspora community – for a time. Most likely our story of the bathhouse took place in Pumbedita, which was where Rabbah lived, and on his way to Kafri, he first traveled through Sura where he met Rav Hamnuna.