Thematic Bible: Mosaic law respecting the firstborn in

"If a man has two wives where one is loved but the other is unloved, and both of them bear him sons, but the firstborn is the son of the unloved wife, then when he bequeaths his possessions to his sons, he must not give preference to the firstborn of the beloved wife over the firstborn of the unloved wife. Instead, he must acknowledge the firstborn of the unloved wife by giving him double of everything he owns, because he is really the first fruit of his father's strength. The right of the firstborn belongs to him."