It is taught in a baraita: If one declares food: Non-sacred, or: The non-sacred, or: Like the non-sacred, then whether he combines that expression with the phrase: That which I eat of yours, or: That which I do not eat of yours, he has not expressed a vow and the food remains permitted. However, if he says: That which I eat of yours shall be considered laḥullin, i.e., not non-sacred, but rather consecrated, the food is forbidden. If he says: That which I do not eat of yours shall be considered laḥullin, the other individual’s food remains permitted to him.

The Gemara analyzes this baraita: Who is the author of the first clause of the baraita? It is Rabbi Meir, who does not hold that from a negative statement you can infer a positive statement. Consequently, even if one said: That which I do not eat of yours shall be considered non-sacred, that does not indicate that what he does eat shall be considered consecrated.

However, say the latter clause of that baraita: If one says: That which I will not eat of yours shall be considered laḥullin, the other individual’s food remains permitted to him. But didn’t we learn in a mishna (13a) that if one says: That which I will not eat of yours shall be considered lakorban, Rabbi Meir prohibits him from eating food belonging to the other individual? Lakorban apparently means la korban, it is not an offering. The reason for this opinion is that his statement indicates that what he does not eat is not an offering, but what he does eat shall be considered an offering. This poses a difficulty for us because Rabbi Meir does not hold that from a negative statement you can infer a positive statement.

And to answer this difficulty, Rabbi Abba said: It is as though he said: It shall be for an offering [lekorban], and therefore I will not eat that which is yours. Here too, when he said: That which I will not eat of yours shall be considered laḥullin, this is what he said to him: It shall not be non-sacred, and therefore I will not eat that which is yours. Consequently, the vow should take effect even according to Rabbi Meir; why does the baraita rule that the vow does not take effect and the food remains permitted?

The Gemara answers: This tanna of the baraita holds in accordance with the opinion of Rabbi Meir in one case and disagrees with his opinion in another. He holds in accordance with his opinion in one case, in that he does not hold that from a negative statement you can infer a positive statement. And he disagrees with his opinion in another case, i.e., in the case of an offering. This tanna holds that if one says: That which I will not eat of yours shall be considered lakorban, he does not mean: It is to be considered an offering and therefore I will not eat from that which is yours. Similarly, in the case in the baraita, the tanna does not hold that the individual means to say: It shall not be non-sacred and therefore I will not eat that which is yours. In order to effect a vow, one must express it clearly.

Rav Ashi said: The apparent contradiction between the baraita and the mishna can be resolved in a different manner. This case in the baraita is where he said: That which I will not eat of yours shall be considered as non-sacred, and that case, where it is forbidden, in accordance with Rabbi Meir’s ruling in the mishna, is where he said: That which I will not eat of yours should not be considered as non-sacred, which indicates: It shall not be considered non-sacred but rather like an offering, and therefore I will not eat it.

§ It is stated in the mishna that if one says that a food item shall be considered not ritually pure, or if he said the food shall be considered an offering that has become ritually impure, left over [notar], or piggul, i.e., an offering that was sacrificed with the intent to consume it after its appointed time, it is forbidden. Rami bar Ḥama raises a dilemma: If one said with regard to a particular item: This is prohibited to me like the meat of peace-offerings after the sprinkling of their blood, what is the halakha? Is this an effective vow, which prohibits the item?

The Gemara responds: If he said it with this formulation, he is associating the object of his vow with a permitted item, as the meat of peace-offerings is permitted to be eaten after the blood is sprinkled on the altar. Consequently, the declaration does not express a vow. Rather, it is a case where he places the meat of peace-offerings following the sprinkling of the blood in one place, and he places an item that is permitted next to it. And he says: This is like that. In this case, what is the halakha? Is he associating the object of his vow with the original forbidden status of the peace-offering before the blood is sprinkled, or is he associating the object of his vow with the current permitted status of the peace-offering?

To resolve this question, Rava said: Come and hear a proof from the mishna: If he said the food shall be considered an offering that has become notar or piggul, i.e. an offering that was sacrificed with the intent to consume it after its appointed time, it is forbidden.