Verses with the word birthright in the Old Testament (8 verses):

Genesis 25:31
And Jacob said, Sell me this day thy birthright.

Genesis 25:32
And Esau said, Behold, I am at the point to die: and what profit shall this birthright do to me?

Genesis 25:33
And Jacob said, Swear to me this day; and he sware unto him: and he sold his birthright unto Jacob.

Genesis 25:34
Then Jacob gave Esau bread and pottage of lentiles; and he did eat and drink, and rose up, and went his way: thus Esau despised his birthright.

Genesis 27:36
And he said, Is not he rightly named Jacob? for he hath supplanted me these two times: he took away my birthright; and, behold, now he hath taken away my blessing. And he said, Hast thou not reserved a blessing for me?

Genesis 43:33
And they sat before him, the firstborn according to his birthright, and the youngest according to his youth: and the men marvelled one at another.

1 Chronicles 5:1
Now the sons of Reuben the firstborn of Israel, (for he was the firstborn; but forasmuch as he defiled his father's bed, his birthright was given unto the sons of Joseph the son of Israel: and the genealogy is not to be reckoned after the birthright.

1 Chronicles 5:2
For Judah prevailed above his brethren, and of him came the chief ruler; but the birthright was Joseph's:)