Abraham is our father = The Jews considered Abraham to be the greatest man to ever live. They figured that since he had found such great favor with God and since they were direct descendents of him, that some of the merit he had earned with God would be passed down to them. (Isaiah 41:8) We see this attitude in Justin Martyr’s “Dialogue With Trypho” the Jew (chapter 140).  He is speaking of the Jewish teachers and says, “they beguile themselves and you, supposing that the everlasting kingdom will assuredly be given to those of the dispersion who are of Abraham after the flesh, although they be sinners, and faithless, and disobedient towards God, which the scriptures have proved is not the case.”

Isaiah 41:8  “But you, O Israel, my servant, Jacob, whom I have chosen, you descendants of Abraham my friend,

The Jews were involved in the error of trying to live on the accomplishments of another. There are those today who try to live on the accomplishments of a parent or relative. They falsely suppose that since their parents are Christians, then they are, too. We can inherit money and we can inherit land, but we can never inherit a relationship with the living God.

There are even churches and denominations today that are trying to live off the achievements of the past. They falsely assume that since God moved in a particular way then, He will do the same now. But God likes to do new things and He is not particularly impressed with our church history or our traditions. Neither a man nor a church can live off the accomplishments of the past.

The Jews had fallen for the earliest temptation of the devil and the one to which he himself fell — pride. They were proud of being descendants of Abraham, but God considers His people to be descendants of another ancestry when they fall away from Him (Ezekiel 16:3). Jesus tells the Jews that they are not Abraham’s descendents in a real sense. If they were, then they would do the things Abraham did.

Ezekiel 16:3  and say, ‘This is what the Sovereign LORD says to Jerusalem: Your ancestry and birth were in the land of the Canaanites; your father was an Amorite and your mother a Hittite.

Lineage to Abraham and the promises given to him are based on faith which is shown by actions, and not upon genetics (Gen 18:19, Rom 4:12, James 2:21-22).

Genesis 18:19  For I have chosen him, so that he will direct his children and his household after him to keep the way of the LORD by doing what is right and just, so that the LORD will bring about for Abraham what he has promised him.”

Romans 4:12  And he is also the father of the circumcised who not only are circumcised but who also walk in the footsteps of the faith that our father Abraham had before he was circumcised.

James 2:21-22  Was not our ancestor Abraham considered righteous for what he did when he offered his son Isaac on the altar?  You see that his faith and his actions were working together, and his faith was made complete by what he did.