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

15 "If a man has two wives, [and] the one [is] loved and the [other] one [is] disliked and the one loved and the one that is disliked have borne for him sons, if it happens [that] the firstborn son {belongs to the one that is disliked}, 16 [nevertheless] {it will be the case that} on the day of bestowing his inheritance upon his sons, he will not be allowed to treat as [the] firstborn son the son of the beloved [wife] {in preference to} the son of the disliked [wife], [who is] the firstborn [son]. 17 But he shall acknowledge the firstborn son of the disliked [wife] {by giving} him a double portion of {all that he has}, for he [is] the firstfruit of his vigor; to him [is] the legal claim of the birthright.