A true Jew is not one who is ethnically descended from Abraham, a true Jew is one who is spiritually descended from Abraham. For truly, there are two bodies that a person has, the fleshly body and the spiritual body. God is not interested in the origin of the fleshly body. God is only interested in the origin of the spiritual body (Philippians 3:3). What does being spiritually descended from Abraham mean? Jesus gives us the answer in John 8:39, where he explains to the ethnic Jews who reject him that they are not descendants of Abraham unless they do the works of Abraham. So you are not a descendant of Abraham until you do the works of Abraham. So what did Abraham do? James 2:23 gives us the answer: Abraham believed God. So Jesus meant that to imitate Abraham's works is to follow God, and whoever does this is truly a descendant of Abraham. But who is God? God is Jesus Christ (John 20:28). So to follow God is to follow Jesus. Whoever follows Jesus (whether Gentiles or ethnic Jews) is a true descendant of Abraham and inherits the promises of Abraham, this is also confirmed by Galatians 3:28-29 and 4:31.Romans 2:28-29
For he is not a Jew who is one outwardly, nor is circumcision that which is outward in the flesh. But he is a Jew who is one inwardly; and circumcision is of the heart, by the Spirit, not by the letter; and his praise is not from people, but from God.
Do you understand? A true descendant of Abraham, a true Jew, is a Christian. Christianity is the true Judaism. The prophets of the Old Testament were all Christians. For to be a Christian is to follow Jesus, and the prophets of the OT followed Yahweh, who is Jesus Himself.
The ethnic Jews who reject Jesus, (which is the majority, because only a few ethnic Jews have accepted Jesus (Romans 9:27)), are not true Jews because they reject Jesus. Jesus called these ethnic Jews children of the devil (John 8:44) who belong to the synagogue of Satan (Rev 2:9).
Moreover, the word "Jew" means "praise Yahweh!". Those who praise Yahweh are the Christians! They are the holy chosen people of God (1 Peter 2:9).
Thank you for reading this far. This knowledge was given to me by Jesus Christ. All praise is due to Him.