15 "Suppose a man has two wives, but he loves one and not the other, and both have given him sons. And suppose the firstborn son is the son of the wife he does not love. 16 When the man divides his inheritance, he may not give the larger inheritance to his younger son, the son of the wife he loves, as if he were the firstborn son. 17 He must recognize the rights of his oldest son, the son of the wife he does not love, by giving him a double portion. He is the first son of his father's virility, and the rights of the firstborn belong to him.
Matthew Henry's Commentary on Deuteronomy 21:15-17
Commentary on Deuteronomy 21:15-17
(Read Deuteronomy 21:15-17)
This law restrains men from disinheriting their eldest sons without just cause. The principle in this case as to children, is still binding to parents; they must give children their right without partiality.