Rav Pappa said yet another version of Reish Lakish’s question. He raised a contradiction between the mishna here involving purses and another mishna referring to a log measure. As we learned in a mishna (Demai 7:4): In the case of one who purchases wine from among the Samaritans [Kutim] and there is reason to suspect that teruma and tithes were not separated, and he cannot separate them before the start of Shabbat, what should he do?

The mishna explains that he proceeds as follows. If, for example, there are one hundred log of wine in the barrels, he says: Two log that I will separate in the future are teruma, as the established average measure of teruma is one-fiftieth; ten log are first tithe; and one-tenth of the remainder, which is nine log, are second tithe. And he desacralizes the second tithe that he will separate in the future, transferring its sanctity to money, and he may drink the wine in the barrel immediately, relying on the separation that he will perform later. This is the statement of Rabbi Meir.

Rabbi Yehuda and Rabbi Yosei and Rabbi Shimon prohibit one from doing so. These three Sages reject the principle of retroactive designation, upon which this method relies, as at the time of the declaration the identity of the particular portions of wine that will be teruma and tithes is unknown. Even according to Rabbi Meir, one can rely on retroactive designation only in a case where he says: That I will separate in the future. In the case of the mishna here, each peruta might be the consecrated one, and one cannot rely on the last one. Rabbi Yoḥanan said to him: The latter clause of the mishna is referring to a situation where one said: This purse will not be exempt from consecration, in which case he is understood as referring to the last peruta left in the purse.