Abraham was a man who believed in God and because of that he was described as the friend of God (James 2:23). God asked him to leave his home and go to a land he would show him, and he would receive it as an inheritance (Hebrews 11:8). God promised that if he obeyed he would also become a great nation and all the families of the earth would be blessed because of him (Genesis 12:1-3). This is the basis of the gospel (Galatians 3:8). If the gospel you believe doesn't include the promises made to Abraham, then it is not the gospel of the Bible.
Abraham and his seed were promised eternal possession of all the land that he could see (Genesis 13:14-17). But in his lifetime Abraham was not given the land (Acts 7:5; Hebrews 11:13). God confirmed the certainty of him receiving it by making an oath (Hebrews 6:13-18). This means that Abraham will receive it in the future. Paul says that the hope of the Fathers of the nation of Israel was the resurrection (Acts 26:6-8). The land will be given to Abraham when Christ returns to raise the dead and set up God's kingdom (Luke 13:28-29).
Although the natural descendants of Abraham are the Jews, the actual seed promised to Abraham is the Lord Jesus Christ (Galatians 3:16). The true children of Abraham are those who have the same faith as Abraham (Galatians 3:7). If we are baptised into Christ we can also inherit the land with Abraham (Galatians 3:26-29).
