כִּי֩ אֶת־הַבְּכֹ֨ר בֶּן־הַשְּׂנוּאָ֜ה יַכִּ֗יר לָ֤תֶת לוֹ֙ פִּ֣י שְׁנַ֔יִם בְּכֹ֥ל אֲשֶׁר־יִמָּצֵ֖א ל֑וֹ כִּי־הוּא֙ רֵאשִׁ֣ית אֹנ֔וֹ ל֖וֹ מִשְׁפַּ֥ט הַבְּכֹרָֽה׃ (ס)
Lecz pierworodnego syna znienawidzonej uzna, aby mu oddać część podwójną wszystkiego, co u niego się znajduje; ponieważ on pierwiastkiem siły jego: jego jest prawo pierworodztwa.
Tosefta Bekhorot
A first-born may not take a double portion of an increase to the value of the property [that accrued] after their father's death. Rebbi says, I say that the first-born may take a double portion of an increase to the value of the property after their father's death, for even his*שאף שלא (Mitzpat Shmuel) [portion] increased along with theirs. How so? He had an animal that was leased or rented to others, [or] pasturing in open territory, [and it gave birth,] the first-born takes a double portion. The foreleg, the maw, and the jaw: Rebbi says, [as to] every item [of inheritance] that the orphans did not [have to] search for after their father's death, the first-born takes a double portion. And he only takes a "double portion as to all that which is found with him" (Deut. 21:17), but if they built a building, or planted a planting, everything [is divided] equally. One who takes a double portion, if he said, "I want that which was not taken, and that which was not given," he has the right to do so.