Deuteronomy 21:15-17

Living Bible

¹⁵ “If a man has two wives but loves one and not the other, and both have borne him children, and the mother of his oldest son is the wife he doesn’t love, ¹⁶ he may not give a larger inheritance to his younger son, the son of the wife he loves. ¹⁷ He must give the customary double portion to his oldest son, who is the beginning of his strength and who owns the rights of a firstborn son, even though he is the son of the wife his father doesn’t love.