Genesis 25:31

31. Jacob said, Sell me ... thy birthright--that is, the rights and privileges of the first-born, which were very important, the chief being that they were the family priests (Ex 4:22) and had a double portion of the inheritance (De 21:17).

Robert Jamieson, A. R. Fausset & David Brown, 1871 · public domain

Verse 31 Sell me this day thy birthright - What the בחרה bechorah or birthright was, has greatly divided both ancient and modern commentators. It is generally supposed that the following rights were attached to the primogeniture: 1. Authority and superiority over the rest of the family. 2. A double portion of the paternal inheritance. 3. The peculiar benediction of the father. 4. The priesthood, previous to its establishment in the family of Aaron. Calmet controverts most of these rights, and with apparent reason, and seems to think that the double portion of the paternal inheritance was the only incontestable right which the first-born possessed; the others were such as were rather conceded to the first-born, than fixed by any law in the family. However this may be, it appears, 1. That the first-born were peculiarly consecrated to God, Exo 22:29. 2. Were next in honor to their parents, Gen 49:3. 3. Had a double portion of their father's goods, Deu 21:17. 4. Succeeded him in the government of the family or kingdom, 2Chr 21:3. 5. Had the sole right of conducting the service of God, both at the tabernacle and temple; and hence the tribe of Levi, which was taken in lieu of the first-born, had the sole right of administration in the service of God, Num 8:14-18; and hence we may presume, had originally a right to the priesthood previous to the giving of the law; but however this might have been, afterwards the priesthood is never reckoned among the privileges of the first-born. That the birthright was a matter of very great importance, there can be no room to doubt; and that it was a transferable property, the transaction here sufficiently proves.

Adam Clarke, 1831 · public domain