We learned on the previous that use of an object belonging to the Temple whose mitzva has already been fulfilled can no longer be considered me’ila (deriving benefit from an object consecrated to the Temple). The Gemara points out that there are a number of other things that belong to the Temple which retain their status even after the mitzva has been completed. They include:
Terumat ha-deshen – the ashes that are removed from the altar at the beginning of the morning Temple service, and
Bigdei kehuna – the vestments worn on Yom Kippur by the kohen gadol, who removes them after he completes the avoda (service).
Consequently, they are two verses that come as one, i.e., they share a unique not found elsewhere. And there is a principle: Any two verses that come as one do not teach, i.e., an analogy may not be derived from these two similar cases. Instead, they are considered exceptional instances that cannot serve as models for other cases.
Generally speaking, the Talmud derives general principles from a passage written in one place and applies them in other places where they logically apply, unless there are specific indications in the pasuk that limit its applicability. In a case like ours, where the Torah specifically teaches the same rule in two places, it is a clear indication that we do not have a general principle, but rather a rule that applies specifically in these two places and nowhere else. There are occasions when the Gemara can prove that the cases are so different from one another (or that each one has a unique quality about it) that we would not be able to extrapolate from one to the other. In such a case, the Gemara would suggest that we can, in fact, apply the rule more generally, even though it is taught by the Torah in both cases.
The Gemara does point out that there is an opinion which allows applying a rule generally even if it does appear in the Torah in two places. According to this opinion, the fact that the rule is repeated twice simply indicates that the Torah wants to emphasize the general applicability of that rule. Even that opinion, though, recognizes that if a rule is repeated three times, then it is limited in its scope and cannot be applied to other cases in the Torah.