When God appeared to Abram at the age of ninety-nine, He established His covenant by declaring that Abram would become the father of many nations. To mark this role, God changed his name to Abraham, stating that He had made him a father of many nations and would make him exceedingly fruitful. From Abraham would come nations and kings, and the covenant would extend as an everlasting agreement to his descendants after him, with God serving as their God and granting them the land of Canaan as an everlasting possession. This promise formed the foundation for the continuing preservation of God's truth and established the line through which the Savior would come. Abraham's position as father of many nations connected directly to his responsibility as patriarch to command his children and household after him, ensuring they kept the way of the Lord by doing righteousness and justice. In this capacity he passed on the education, understanding, and wisdom received from God, enabling the fulfillment of the covenant that all families of the earth would be blessed through him. The same covenant later confirmed to his Seed, identified as Christ, underscored Abraham's central place in the divine purpose that extended from the days after the Flood through the patriarchal line to future generations.

In Genesis 17:5 God changed Abram ("exalted father") to Abraham ("father of many nations") as a sign and seal of his altered role in the purpose God was working out. Sarai's name was likewise changed to Sarah, whose root idea of ruling as a queen points to her role as matriarch, "a mother of nations" from whom kings of peoples would come. The name change therefore shows the covenant was made with both Abraham and Sarah, not merely a male, a point echoed in Galatians 3:28-29, where all in Christ are Abraham's seed and heirs according to the promise. Abraham's patriarchal rule is also seen in the many nations God used him to shape. His visit to Egypt coincided with its reunification under Mentuhotep II. Drawing on Josephus, Abraham is said to have refuted the Egyptians' quarreling religious views and taught them arithmetic and astronomy, laying groundwork for the commercial, technological, and cultural strength of Dynasty 12, the nation that later sheltered Israel's growth under Jacob and Joseph. His rout of the four Assyrian kings in Genesis 14 then plunged Assyria into chaos and kept it from rising as a power until about 700 BC. Both works prepared the way for his descendants to become a nation in Egypt.

God made Abraham a twofold promise. The material promise was that he would be the father of many nations and that kings would descend from him, and that his progeny would inherit the land of Canaan, stretching from the Nile to the Euphrates. The more important promise was spiritual: in his Seed, Jesus Christ, all the nations of the earth would be blessed. The promises were given first to Abraham and his Seed, Christ, and then extended to all whom God now calls to salvation. Abraham's physical descendants, the nation of Israel, inherited Canaan, which was a type of Abraham's spiritual descendants inheriting the whole earth (Romans 4:13). Those who belong to Christ through faith are counted as Abraham's spiritual descendants, regardless of race or sex, because they exhibit his faith and righteousness. They therefore inherit the same promises made to him. Abraham's fatherhood thus reaches beyond bloodline to all true Christians, who as co-heirs with Christ will reign on the earth under Him.

God gave Abram his new name at ninety-nine years old, before the promised son was born: "No longer shall your name be called Abram, but your name shall be Abraham; for I have made you a father of many nations." The change fits the man and what he would be known for forever, since Abraham means father of many nations or multitudes. God made His covenant with Abraham, promised to multiply him exceedingly, and said nations and kings would come from him. Sarai likewise became Sarah, meaning princess, because she would be a mother of nations and kings of peoples would descend from her. The line would come through Isaac, not Ishmael. The namer is superior to the one named and can discern true character, so any name God gives is a true name, as with Babel, which means confusion, and with Jesus, the Savior. Abraham's new name is such a name: it identifies him and also looks ahead to his descendants. A name can denote continuance and progeny as well as identity, so the name Abraham carries the whole line of nations that would come from him.