Mishnayos Demai Perek 7 Mishnah 4

הלוקח יין מבין הכותים – before they (i.e., the Rabbis) decreed regarding their wine, their wine was definitely eatables forbidden pending the separation of priestly gifts (i.e., טבל), but here we are speaking about someone who purchases on the Eve of the Sabbath at twilight or who purchases while it is still daytime and forgot to separate [tithes] until twilight, and then it is prohibit to separate [tithes] as it is taught in the Mishnah [Tractate Shabbat, Chapter 2, Mishnah 7]: “If it is a matter of doubt whether or not it is getting dark, they do not tithe that which is certainly not tithed produce,” therefore it is forbidden to establish for it a place for the establishment of a place is considered like setting something aside and that is forbidden at twilight, and because of this it (i.e., our Mishnah) does not teach in the concluding clause “and Second Tithe is redeemed for coins,” for since it is not permitted to establish for it a place to the north or to the south, it is impossible to redeem it, but [only] to designate for it a name, that he said, “that in the future I will separate,” is permitted, for all that much is not decreed at twilight.

שאני עתיד להפריש – here it does not teach, “that I will separate tomorrow,” as it is taught above (see Chapter 7, Mishnah 1) regarding inviting one’s fellow over, for especially, when specifically when he doesn’t make fit for use by separating the priestly gifts other than what he is eating and drinking, they (i.e., the Rabbis) permitted him to separate for the morrow from the left-over of his food and his drink that remains on the rim of the cup, but to make fit for use all of the leather bottle/skin on Shabbat, they (i.e., the Rabbis) did not permit to him. But here he does not designate a name for the heave-offering of the tithe as in the segment dealing with doubtfully tithed produce as above, concerning the case of someone who invites his fellow (see again, Tractate Demai, Chapter 7, Mishnah 1) because regarding doubtfully tithed produce that he tithes, and they are his, he designates them for the heave-offering of the tithe in order to make things legally fit by giving priestly dues for the tithe and to consume it, but here, which is certainly eatables forbidden pending the separation of priestly gifts, he must give the [First] Tithe to the Levite and the Levite will designate it for the heave-offering of the tithe.

ועשרה מעשר ראשון ותשעה מעשר שני – not exactly, for after he separated from one-hundred, two LOGS (i.e., 1/50th - the Great Terumah for the Kohen), and there remains ninety-eight, the [First] Tithe will not be other than ten LOGS less one-fifth and Second Tithe [will be] eight LOGS and eight tenths and one fifth of a tenth.

מיחל ושותה (he regards as unconsecrated produce)– he begins and drinks. Another explanation: he pours and drinks. [The word] "מיחל" is like מיהל – the language from (Isaiah 1:22): “[Your silver has turned to dross;] Your wine is cut with water.” But the anonymous Mishnah comes from Rabbi Meir who said that even according to the Torah there is a choice, and that which remains in the bottom of the cup it is as It was separated from the outset. But it is not the Halakha but rather we hold according to the Rabbis who state that there is a choice/subsequent selection (i.e., the legal effect resulting from an actual selection or disposal of things previously undefined as to their purpose), but according to the Torah, there is no choice, and therefore, regarding something that is definitely eatables forbidden pending the separation of priestly gifts (i.e., טבל), he should not eat nor drink until he separates [tithes].