Nedarim 12A

והא נותר ופיגול לאחר זריקת דמים הוא.

But notar and piggul are conditions that apply after the sprinkling of the blood, when the prohibition against misusing consecrated property, which the individual is attempting to extend to a permitted item, no longer applies. Since the vow takes effect, this proves that the individual is associating the object of his vow with the original forbidden status of the offering.

אמר ליה רב הונא בריה דרב נתן: בנותר של עולה. אמר ליה: אם כן, ליתני בבשר עולה!

Rav Huna, son of Rav Natan, said to him: It is possible to say that it is speaking here about notar of a burnt-offering. Since a burnt-offering may not be eaten even after its blood is sprinkled, the original prohibition against misusing consecrated property continues to apply to the meat of this offering. Rava said to Rav Huna, son of Rav Natan: If so, let it teach explicitly that the individual referred to the meat of a burnt-offering.

לא מיבעיא קאמר: לא מיבעיא ״בשר עולה״ דאסור, דהא בקרבן קא מתפיס, נותר ופיגול דעולה איצטריכא,

The Talmud responds: The tanna is speaking utilizing the style of: It is not necessary. It is not necessary to state that if one associates the object of his vow with meat of a burnt-offering, it is forbidden, as he extends the status of an offering to the other item. However, if one extends the status of notar and piggul of a burnt-offering, it is necessary to say that the other item is forbidden.

סלקא דעתך אמינא כאיסור נותר, כאיסור פיגול, והוה ליה כמתפיס בדבר האסור, ולא מיתסר, קא משמע לן.

It could enter your mind to say that the individual intended to declare the item forbidden like the prohibition of notar or like the prohibition of piggul, and this would be like one who associates the object of his vow with an item that is forbidden by the Torah rather than an item forbidden by means of a vow. Consequently, the item is not forbidden, as one can take a vow by associating the object of his vow with a forbidden item only if that item is itself prohibited due to a vow. The Mishnah therefore teaches us that his intention is to transfer the prohibition of the offering, and the vow takes effect.