Deuteronomy 21:15-17 - The Right Of The Firstborn

¹⁵ If a man shall have two wives, one beloved, and another hated, and they have borne him children, both the beloved and the hated; and if the first-born son be hers that was hated: ¹⁶ Then it shall be, when he maketh his sons to inherit that which he hath, that he may not prefer the son of the beloved first-born, before the son of the hated, which is indeed the first-born: ¹⁷ But he shall acknowledge the son of the hated for the first-born, by giving him a double portion of all that he hath: for he is the beginning of his strength; the right of the first-born is his.