Rav Pappi and Rav Pappa disagree with regard to Rava’s intention. One Sage, Rav Pappi, holds that he has done nothing with regard to his brother’s portion, as he had no right to sell it; with regard to his own additional portion, the sale was valid, as it was in his possession even before the division of the property. And one Sage, Rav Pappa, holds that he has done nothing with regard to all of the property, as he does not possess the additional portion before the property is divided between the brothers.

The Gemara notes that they sent a ruling from there, Eretz Yisrael: A firstborn who sold his additional portion before the division of the property has done nothing. Apparently, the Sages of Eretz Yisrael hold that a firstborn does not have a right to his additional portion before the division. But the halakha is that a firstborn has a right to his additional portion before the division.

The Gemara relates: Mar Zutra of the house of Rishba, who was a firstborn, divided a basket of peppers from the estate of his father with his brothers equally. He came before Rav Ashi to claim a double portion of the rest of the estate. Rav Ashi said to him: Since you relinquished your additional portion with regard to some of the estate, you have relinquished your additional portion with regard to all of the property, as a firstborn has a right to his additional portion before the division.

MISHNA: In a case of one who says: So-and-so, my firstborn son, will not take a double portion of my estate; or one who says: So-and-so, my son, will not inherit my estate among his brothers, he has said nothing, as he has stipulated counter to that which is written in the Torah.

With regard to one on his deathbed who apportions his property orally, granting it to his sons as a gift, and he increased the portion given to one of his sons and reduced the portion given to one son, or equated the portion of the firstborn to the portions of the other sons, his statement stands. But if he said that they will receive the property not as a gift but as inheritance, he has said nothing. If he wrote in his will, whether at the beginning, or in the middle, or at the end, that he is granting them the property as a gift, his statement stands.

GEMARA: The Gemara suggests: Let us say that the mishna is not in accordance with the opinion of Rabbi Yehuda, as if it is in accordance with the opinion of Rabbi Yehuda, doesn’t he say elsewhere that if one stipulates counter to that which is written in the Torah with regard to monetary matters, his stipulation stands?

As it is taught in a baraita (Tosefta, Kiddushin 3:7): If one says to a woman: You are hereby betrothed to me on the condition that you have no ability to claim from me food, clothing, and conjugal rights, she is betrothed and his stipulation is void; this is the statement of Rabbi Meir. Rabbi Yehuda says: With regard to monetary matters, such as food and clothing, his stipulation stands, despite being counter to that which is written in the Torah. According to the opinion of Rabbi Yehuda, one should be able to stipulate that his firstborn son not receive a double portion, or that one of his sons not inherit from him at all, as inheritance is a monetary matter.

The Gemara rejects this suggestion: Even if you say that the mishna is in accordance with the opinion of Rabbi Yehuda, there, the woman knew of his stipulation and waived her rights. Therefore, the stipulation stands. Here, the son whose portion was reduced did not waive his portion. Therefore the stipulation is not valid.

§ Rav Yosef says that if a man says: So-and-so is my firstborn son, the son takes a double portion of his inheritance based on this testimony. If he says: So-and-so is a firstborn, the son does not take a double portion, as perhaps the man was saying that the son is his mother’s firstborn but not his own firstborn.

The Gemara relates: There was a certain man who came before Rabba bar bar Ḥana and said to him: I know that this man is a firstborn. Rabba bar bar Ḥana said to him: From where do you know? He answered: Because his father would call him a foolish firstborn. Rabba bar bar Ḥana replied: Perhaps he is his mother’s firstborn, as any firstborn of a mother is also called a foolish firstborn.

The Gemara relates: There was a certain man who came before Rabbi Ḥanina and said to him: I know that this man is a firstborn. Rabbi Ḥanina said to him: From where do you know? He said to Rabbi Ḥanina: Because when people would come before his father to obtain a cure for their ailing eyes, he would say to them: Go to my son Shikhḥat, as he is a firstborn and his saliva heals this ailment.

The Gemara asks: But perhaps he is his mother’s firstborn? The Gemara answers: It is learned as a tradition that the saliva of a father’s firstborn heals this ailment but the saliva of a mother’s firstborn does not heal this ailment.

§ Rabbi Ami says: In the case of one whose sexual organs are indeterminate [tumtum] and whose skin became perforated so that his genitals were exposed and he was found to be a male, he does not take a double portion of his father’s estate. As the verse states: “And if the firstborn son was [vehaya] hers that was hated” (Deuteronomy 21:15), which is interpreted to mean that he is not considered a firstborn unless he is recognized as a son, i.e., male, from the moment of his coming into being [havaya], i.e., his birth.

Rav Naḥman bar Yitzḥak says: A tumtum who was found to be male is also not judged as a stubborn and rebellious son, as the verse states: “If there will be [yihyeh] to a man a stubborn and rebellious son” (Deuteronomy 21:18), which is interpreted to mean that one is not judged in this manner unless he is recognized as a son from the moment of his coming into being.