Genesis 17:6

And I will make thee exceeding fruitful, and I will make nations of thee, and kings shall come out of thee.

The promise was spoken as part of God's everlasting covenant with Abraham and his seed, in which God would be their God, given after nearly twenty-five years in Canaan and later confirmed to Isaac. It promises that Abraham would be made exceedingly fruitful with many descendants, becoming a father of many nations, and that nations and kings would come from him and arise among his descendants. The change of Abram to Abraham, meaning father of a great multitude, was given in token of the fulfillment of this covenant, and Sarai to Sarah, meaning princess, because she would be a mother of nations with kings of people from her.

Taught to Esau and Jacob as bound up with the birthright and held as the great object of hope, the promise of nations and kings meant both an inheritance of worldly wealth and spiritual pre-eminence, in that its holder would be priest of his family and the Redeemer of the world would come in the line of his posterity. Circumcision was given at that same time as a seal of the righteousness of the faith Abraham already had while uncircumcised, to be observed by him and his descendants as a token that they were devoted to God's service, separated from idolaters, and accepted as God's peculiar treasure. It was the sign and pledge of their obligation to be separate from other nations and faithful to God. Abraham was commanded to walk before God and be perfect, and keeping separate in this way would help his descendants resist idolatry and preserve their holy character.

Inheriting its blessings required devoting life to the service of God and obeying the divine requirements and law of God as Abraham did, including consulting the will of God in marriage, family relations, and public life. Specifically it required not contracting marriages with the heathen, lest reverence for God and His holy law be lost and they be tempted into sinful practices and seduced into idolatry. Isaac presented Esau as the eldest entitled to this birthright, but Esau had no love for devotion or religious life and regarded its requirements as unwelcome restraint and bondage, desiring self-indulgence, liberty, power, riches, feasting, and wild freedom, while Rebekah held from the angel's words that the heritage of divine promise was intended for Jacob.