An excerpt from "Bible Tools.org" entitled, "What the Bible says about God's Promises to Abraham" by Earl L. Henn, states: "God made a twofold promise to Abraham. The first was a material promise that he would be the father of many nations and that kings would descend from him. God promised him that his progeny would inherit the land of Canaan, an expanse that He defined as stretching from the Nile to the Euphrates rivers. The second, but more important, promise was spiritual. God promised Abraham that in his Seed all the nations of the earth would be blessed. This promise encompasses the life and work of Abraham's best known and most revered descendant, Jesus Christ.
This promise was later extended to include the inheritance of the whole world (Romans 4:13)." This article may be viewed at: What the Bible says about God's Promises to Abraham/bibletools.org
Reference: Romans 9:5