Genesis 17:7, commentary and pictures

God appeared as the Almighty God after Abraham had lived nearly twenty-five years in Canaan, commanding him to walk perfectly before Him, renewing the promise that he would be a father of many nations, and promising to multiply him greatly. In token of its fulfillment Abram's name was changed to Abraham, signifying father of a great multitude, and Sarai's name to Sarah, signifying princess, because she would be a mother of nations with kings of people coming from her. By this word He established an everlasting covenant between Himself and Abraham and his seed after him in their generations, promising to be a God to Abraham and to his seed.

The covenant seed is not Ishmael but Isaac, for though Abraham after Ishmael's birth still thought the promised many nations might come through Ishmael, God clarified that Sarah would bear Isaac and established the everlasting covenant with Isaac and his descendants. At that time circumcision was given as the sign, seal, and token of the covenant, sealing the righteousness of the faith Abraham already had while uncircumcised, marking him and his descendants as devoted to God's service, separated from idolaters, and accepted as His peculiar treasure, and pledging them to fulfill their part of the covenant. That human part required separation from other nations, faithfulness to God, perfection, and obedience to the divine requirements, especially not contracting marriages with the heathen, because such unions would cause loss of reverence for God and His holy law and lead into sinful practices and idolatry.

Failure to keep separate weakened holy character and led toward idolatry, yet God did not forsake Abraham's descendants in Egypt because of His covenant, but allowed them to be oppressed so they would turn to Him and choose to obey Him. The covenant is the covenant of grace renewed to Abraham and part of an eternal provision given hundreds of years before Christ came: it pointed to Christ, whom Abraham trusted for forgiveness, offered pardon and God's help for obedience through faith in Christ, upheld God's law, and held out eternal life on condition of faithfulness, so that those who obey and through grace become holy and blameless may be God's children. The promise to be a God to Abraham and his seed was held as the great hope and taught to succeeding generations as the birthright, which included worldly wealth and spiritual pre-eminence, making its holder priest of his family and the one in whose posterity the Redeemer of the world would come, and which required devoting life to God's service.