Deuteronomy 21:15-17
Read Deuteronomy 21 in full →15“If a man has two wives, the one loved and athe other 1unloved, and both the loved and the 2unloved have borne him sons, if the firstborn son belongs to the 3unloved, 16then it shall be in the day he 1wills what he has to his sons, he cannot make the son of the loved the firstborn before the son of the 2unloved, who is the firstborn. 17“But he shall recognize the firstborn, the son of the 1unloved, by giving him a double portion of all that 2he has, for he is the afirst of his vigor; bthe legal judgment for the firstborn belongs to him.