כִּי֩ אֶת־הַבְּכֹ֨ר בֶּן־הַשְּׂנוּאָ֜ה יַכִּ֗יר לָ֤תֶת לוֹ֙ פִּ֣י שְׁנַ֔יִם בְּכֹ֥ל אֲשֶׁר־יִמָּצֵ֖א ל֑וֹ כִּי־הוּא֙ רֵאשִׁ֣ית אֹנ֔וֹ ל֖וֹ מִשְׁפַּ֥ט הַבְּכֹרָֽה׃ (ס)
Kundi kikilalanin niya bilang panganay ang anak ng kinapopootan, sa pamamagitan ng pagbibigay sa kanya ng dalawang bahagi sa lahat ng nasa kanyang pag-aari, sapagkat siya ang unang bunga ng kanyang lakas; sa kanya ang karapatan ng pagkapanganay.
Mishnah Kiddushin
If a man declares, “this son of mine is a mamzer,” he is not believed. And even if both [the husband and wife] say about the fetus inside her, “it’s a mamzer” they are not believed. Rabbi Judah says: they are believed.
Mishnah Ketubot
If he did not write for her, “The male children that will be born from our marriage shall inherit the money of your ketubah over and above their shares with their brothers”, he is nevertheless liable, because [this clause] is a condition laid down by the court.
Mishnah Bekhorot
The first-born takes a double share of the father's estate but he does not take a double share of the mother’s estate. He also does not take a double share of the improvement in the value of the estate. Nor from what will fall due [to the estate] as he does of what is held in possession. Nor can a woman claim with her ketubah [from these], Nor can daughters claim their support. Nor can a yavam make a claim [from these]. None of these take from the improvement in the value of the estate, nor of what will fall to the estate as they do of what is now held in possession.