15 If a man has two wives, one loved and the other disliked, and they both have borne him children, and if the firstborn son is the son of the one who is disliked, 16 Then on the day when he wills his possessions to his sons, he shall not put the firstborn of his loved wife in place of the [actual] firstborn of the disliked wife--her firstborn being older. 17 But he shall acknowledge the son of the disliked as the firstborn by giving him a double portion of all that he has, for he was the first issue of his strength; the right of the firstborn is his.