KJ2000(i)
16 Then it shall be, when he makes his sons to inherit that which he has, that he may not make the son of the beloved firstborn before the son of the hated, who is indeed the firstborn:
17 But he shall acknowledge the son of the hated as the firstborn, by giving him a double portion of all that he has: for he is the beginning of his strength; the right of the firstborn is his.