Moisés
The Law of the Firstborn's Inheritance
The law states that when a man has two wives, one he loves and one he does not love, and both have borne him sons, and the firstborn is the son of the wife he does not love, he may not give the birthright to the son of the wife he loves on the day he distributes his inheritance. He must recognize the firstborn as the son of the unloved wife and give him a double portion of all that he has, for he is the firstfruits of his strength, and the right of the firstborn belongs to him.
Deuteronomio 21,15-17
15If a man has two wives, one loved and the other unloved, and both bear him sons, but the firstborn is the son of the unloved wife,
כִּֽי־תִהְיֶ֨יןָ לְאִ֜ישׁ שְׁתֵּ֣י נָשִׁ֗ים הָאַחַ֤ת אֲהוּבָה֙ וְהָאַחַ֣ת שְׂנוּאָ֔ה וְיָֽלְדוּ־ל֣וֹ בָנִ֔ים הָאֲהוּבָ֖ה וְהַשְּׂנוּאָ֑ה וְהָיָ֛ה הַבֵּ֥ן הַבְּכ֖וֹר לַשְּׂנִיאָֽה׃
16then when he divides his property among his sons, he may not treat the son of the wife he loves as the firstborn in place of the actual firstborn, the son of the wife he does not love.
וְהָיָ֗ה בְּיוֹם֙ הַנְחִיל֣וֹ אֶת־בָּנָ֔יו אֵ֥ת אֲשֶׁר־יִהְיֶ֖ה ל֑וֹ לֹ֣א יוּכַ֗ל לְבַכֵּר֙ אֶת־בֶּן־הָ֣אֲהוּבָ֔ה עַל־פְּנֵ֥י בֶן־הַשְּׂנוּאָ֖ה הַבְּכֹֽר׃
17He must acknowledge the firstborn, the son of the unloved wife, by giving him a double share of everything he owns, for that son is the firstfruits of his strength; the right of the firstborn belongs to him.
כִּי֩ אֶת־הַבְּכֹ֨ר בֶּן־הַשְּׂנוּאָ֜ה יַכִּ֗יר לָ֤תֶת לוֹ֙ פִּ֣י שְׁנַ֔יִם בְּכֹ֥ל אֲשֶׁר־יִמָּצֵ֖א ל֑וֹ כִּי־הוּא֙ רֵאשִׁ֣ית אֹנ֔וֹ ל֖וֹ מִשְׁפַּ֥ט הַבְּכֹרָֽה׃ ס