Scofield Reference Notes (1917 Edition)Chapter 25
25:1 Then again Abraham took a wife, and her name was Keturah.
25:25 And the first came out red, all over like an hairy garment; and they called his name Esau.
As Sarah stands for "the mother of us all," i.e. of those who, by grace, are one with the true Son of promise, of whom Isaac was the type John 3:6-8; Galatians 4:26,28,29; Hebrews 2:11-13 and joint heirs of His wealth ; Hebrews 1:2; Romans 8:16,17, so Keturah (wedded after the full blessing of Isaac) and her children by Abraham may well stand for the fertility of Israel the natural seed, Jehovah's wife Hosea 2:1-23 after the future national restoration under the Palestinian covenant.
(See Scofield "Deuteronomy 30:3") .
25:31 And Jacob said, Sell me this day thy birthright.
Esau stands for the mere man of the earth. Hebrews 12:16,17. In many respects a nobler man, naturally, than Jacob, he was destitute of faith, and despised the birthright because it was a spiritual thing, of value only as there was faith to apprehend it.
The "birthright" had three elements:
(1) Until the establishment of the Aaronic priesthood the head of the family exercised priestly rights.
(2) The Abrahamic family held the Edenic promise of the Satan-Bruiser Genesis 3:15. --Abel, Seth, Shem, Abraham, Isaac, Esau.
(3) Esau, as the firstborn, was in the direct line of the Abrahamic promise of the Earth-Blesser Genesis 12:3.
For all that was revealed, in Esau might have fulfilled those two great Messianic promises. This birthright Esau sold for a momentary fleshly gratification. Jacob's conception of the birthright at that time was, doubtless, carnal and inadequate, but his desire for it evidenced true faith.