Support #1: This is also the reason for one who is Matfis in Terumas Lachmei Todah after Zerikah, and one who is Matfis in Bechor after Zerikah;

He is not forbidden, like is proven from the Sugya below, even though they are forbidden to Zarim. Since they are permitted to Kohanim, [this shows that] the Isur is not due to his vow.

If they were due to his vow, they should be forbidden to everyone! Rather, it is an Isur that the Torah imposed on it. He is Matfis in Davar ha'Asur.

Support #2: This is also the reason why one who is Matfis in Chalas Aharon and his [Aharon's, i.e. Kohanim's] Terumah, he is permitted. The Isur is not due to his vow. Rather, it is a Gezeras ha'Kasuv. So it seems to me.

Explanation: Granted, if you will say that we do not discuss an Olah, it mentioned Nosar to teach that he is Matfis in the initial Isur;

However, if you will say that we discuss an Olah, what is the Chidush of Nosar? Still, his Neder was not uprooted. If so, it should teach meat of an Olah!

Implied question: Based on what I explained in our Mishnah, that for Nosar and Pigul R. Yehudah does not require a Kaf of comparison...

We should have answered this is why it taught Nosar, and not meat of an Olah, to teach that these forbid even without a Kaf of comparison!

Answer: The Gemara gave a better answer.

Explanation: He says on Sunday, which is like the day that his father died according to the count of months, e.g. it was Sunday of the first week of Nisan;

[He said] 'this day will be Alai like Sunday of the first week of Nisan."

Inference: There are many permitted Sundays, yet it teaches that he is forbidden! This teaches that he is Matfis in the initial Isur.

Source: The Gemara infers that this is the case, for if he explicitly said that this day is like the day his father died, obviously he is forbidden!

Rather, surely he said "this day will be Alai like Sunday of the first week of Nisan." The Chidush is, even though we could have said that he is Matfis in Heter...

(We do not.) Since it is now the same day according to the count of months, like the day his father died, and he is Matfis and says "this day will be Alai like Sunday", he is Matfis in the initial Isur, and he is forbidden.

Explanation: The case is every Sunday that passed was like the day his father died were forbidden to him due to a Neder;

Therefore, we cannot learn this law from here and say that it teaches this Chidush, for here there are no days of Heter at all.

Explanation #1: This Sugya is truncated. The Gemara did not explain if so, what does it comes to teach us? Rather, it relied on the Sugya in Shevuos (20a);

We say there exactly like here. Shmuel said that all the days that passed from that day were forbidden to him due to a Neder;

Afterwards we ask "the day that his father died? This is obvious!", and answer that the day Gedalyah was killed is the Chidush.

We ask that also this is obvious, and answer that one might have thought that since even if he had not vowed, it is forbidden mid'Rabanan, even when he vows, his vow does not take effect, and he is not Matfis in a vow. The Beraisa teaches that this is not so. So it seems to me.

Explanation #2: Alternatively, this Sugya holds that even though it is unlike a Korban, which is forbidden to everyone, for here he forbids only to himself, even so, it is called Matfis in Davar ha'Nadur.

From the conclusion in Shevuos we learn to one who vowed [not to eat] cheese of Nochrim or their wine, or the fat of Gid ha'Nasheh, and he was Matfis in them. He is Matfis in the Neder, and he is forbidden.

Implied question: Really, we could have answered that he separated them after they were baked, before Zerikah;

They were baked even before Shechitah of the Zevach (Todah), for it says in Menachos (78b) that if the Zevach was slaughtered before the faces of the bread formed a crust, [the bread] did not become Kodesh.

Answer: Rather, since we bring a proof from Rav Tuvi that he can separate before Zerikah, and Rav Tuvi discusses when he separated them when they were kneaded (before they were baked), also here we discuss when he separated them when they were kneaded.

Explanation: "If it is before Zerikah" means that he said so explicitly.

Assertion: It seems to me that really, we could have asked "if he said 'it is Alai like a Bechor' Stam, what is the reason for the one who permits?'

Even if we say that he is Matfis in Heter, anyone who says Stam, he is Matfis in the initial Isur.

Source - Implied question: Our Mishnah teaches "Chatas, Todah, Shelamim, he is forbidden." Why don't we infer from it in our Sugya that he is Matfis in the initial Isur?

Answer: Since we needed to say "if it is after Zerikah, what is the reason for the one who forbids?", we said also "if it is before Zerikah, what is the reason for the one who permits?" However, also Stam was difficult.

Explanation: Even though he is obligated to bring them, they are called Davar ha'Nadur more than Bechor.