Rabba taught that when something is stolen and then it is changed in such a manner that it will not revert to its original state, the person who stole it takes possession of it and he no longer is obligated to return the stolen object, rather he will have to pay its value (at the time it was stolen) to the original owner. While this is true for an object that undergoes a shinui ma’aseh – a change in its physical form – will it also be true when there is only a shinui ha-shem – only its name changes?
Rava says that this was a question that both Rabba and Rav Yosef could not answer until Rav Yosef was appointed to head the academy, and he taught that a change in name is significant, just as a change in the actual object is significant. Just as we recognize that wood changes to be a utensil, similarly we recognize that a piece of leather can become a chair covering (even though there was no physical change in the object).
Rav Yosef’s appointment to head the yeshiva in Pumbedita is described in Massekhet Horayot and Massekhet Berakhot. When Rav Yehuda passed away, the two obvious candidates to replace him were Rabba and Rav Yosef. Rabba, who was the younger of the two, was known for his sharp, insightful analysis, while Rav Yosef was known for his wide ranging knowledge. In an attempt to decide who should be chosen, the following question was sent to the Sages of the Land of Israel: “Which is better – Sinai (i.e. knowledge) or oker harim (literally, ‘one who uproots mountains’ – i.e. sharp insight)?”
Although the response from Israel was that “Sinai” was more essential, still Rav Yosef declined the position, and for the 22 years that Rabba was in the position of Rosh Yeshiva, Rav Yosef declined all honors. Only after Rabba’s passing did Rav Yosef accept the position.