The promise made to Abraham was fulfilled in Jesus Christ (Galatians 3). God’s covenant with Abraham was with Abraham and his seed which is Christ. This covenant was given to Isaac and Jacob also. Interestingly neither Abraham, Isaac, or Jacob ever inherited the physical land of Israel (Acts 7:5; Hebrews 11:8-13).
The land promise was for the descendants of Abraham, Isaac, and Jacob, and was fulfilled under the ministry of Joshua (Joshua 14:1; Psalm 105:44). God’s covenant with Israel regarding the ongoing inheritance in the land was dependent on observance of the law covenant given through Moses (Deuteronomy 27-30; Psalm 105:44-45).
The law covenant was accompanied with a curse which for the nation as a whole would result in banishment (or disinheritance) from the land (Deuteronomy 27-30; Daniel 9:11). One cannot separate the land promises to Abraham from the law covenant and remain true to the narrative. They are inseparable.
Furthermore, Israel’s land inheritance coincided with physical circumcision which was the “sign” of the covenant. All who were uncircumcised were to be cut off (Genesis 17:7-14).
Paul tells us that physical circumcision has been made of no effect and the law abolished. In Christ it is circumcision of the heart (spiritual circumcision) that matters and in Christ all families of the earth become the children of Abraham.
God’s promise to the Messiah was; “Ask of me, and I shall give thee the heathen for thine inheritance, and the uttermost parts of the earth for thy possession” (Psalm 2:8).
The land promises given to Abraham were conditional, being dependent on physical circumcision and obedience to the law. Israel in the flesh failed to keep the law and inherited the curse. Jesus the Messiah, redeemed the people of Israel from the curse of the Law, and in doing so the promise expanded beyond the physical borders of Israel to all nations for the blessing of Abraham was now to come on the Gentiles (Galatians 3:13-14).
The uttermost parts of the earth has become the possession of the children of Abraham and in Christ, Abraham has now become the heir of the world (Romans 4:13).
The fulfillment of God’s promise to Israel in the Messiah did not leave them as a physical nation in the land of Israel. The fulfillment of God’s promise to Israel made them a spiritual nation of people in all nations throughout the whole world, beginning in Jerusalem (Acts 1:6-8; 2:1-11).
Now, there is a new covenant with the house of Israel and the house of Judah (Jeremiah 31:31-34; Hebrews 8:6-13). This new covenant has replaced the former which defined Israel as a physical nation and of which the land of Canaan was the inheritance. In this new covenant the Gentiles from all nations are grafted in with believing Jews as the true Israel of God, and made fellow heirs, and of the same body, and partakers of God’s promise in Christ by the gospel (Romans 11: Ephesians 2:11 -3:6).