6 Sept. Paul explains how God's covenant promise is fulfilled
"So what can we say that Abraham, the father of our people, learned about faith? If Abraham was made right by the things he did, he had a reason to boast. But this is not God's view, because the Scripture says, 'Abraham believed God, and God accepted Abraham's faith, and that faith made him right with God'." [Genesis 15:6]
"When people work, their pay is not given as a gift, but as something earned. But people cannot do any work that will make them right with God. So they must trust in him, who makes even evil people right in his sight. Then God accepts their faith, and that makes them right with him..."
"Is this blessing only for those [Jews] who are circumcised or also for those [Gentiles] who are not circumcised? We have already said that God accepted Abraham's faith and that faith made him right with God. So how did this happen? Did God accept Abraham before or after he was circumcised? It was before his circumcision."
"Abraham was circumcised to show he was right with God through faith before he was circumcised. So Abraham is the father of all those who believe but are not circumcised; he is the father of all believers who are accepted as being right with God. And Abraham is also the father of those who have been circumcised and who live following the faith that our father Abraham had before he was circumcised."
"Abraham and his descendants received the promise that they would get the whole world. He did not receive that promise through the [Jewish] law, but through being right with God by his faith... So people receive God's [covenant] promise by having faith. This happens so the promise can be a free gift."
(Romans 4:1-16)
In this section of his letter, Paul explains how Abraham, the father of the Jewish people, moved from Harran in Mesopotamia to Canaan (Palestine) because he had faith in God’s promise (see Genesis 12:1-3).
In the same way, any believer – Jew or Gentile – can be forgiven and receive God’s blessings through their faith that Jesus died for their sins and rose again from the dead.
It was because of Abraham’s faith that God promised to make him ‘the father of many nations’, not because he had been circumcised or performed the ‘works’ laid down in the Jewish law.
In the same way, God will continue to be faithful to his covenant promise to Abraham by including Gentiles as well as Jews in a single, united, worldwide family.
You can read more about God's promise to Abraham in the Old Testament in Genesis 17:1-27 or @ The Bible Journey | The birth of Ishmael
The photo (by Glumik) shows Harran, from where Abraham moved to Canaan to become "the father of many nations".