17 "But he shall acknowledge the firstborn , the son of the unloved , by giving him a double portion of all that he has , for he is the beginning of his strength ; to him belongs the right of the firstborn .

Matthew Henry's Commentary on Deuteronomy 21:17

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.