15 If a man has two wives, one greatly loved and the other hated, and the two of them have had children by him; and if the first son is the child of the hated wife: 16 Then when he gives his property to his sons for their heritage, he is not to put the son of his loved one in the place of the first son, the son of the hated wife: 17 But he is to give his first son his birthright, and twice as great a part of his property: for he is the first-fruits of his strength and the right of the first son is his.
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.