Rev 2:9: “I know your works, tribulation, and poverty (but you are rich); and I know the blasphemy of those who say they are Jews and are not, but are a synagogue of Satan.”
Rev 3:9: “Indeed I will make those of the synagogue of Satan, who say they are Jews and are not, but lie–indeed I will make them come and worship before your feet, and to know that I have loved you.”
Concerning the “group calling themselves Jews, but are not Jews” or “the Synagogue of Satan”. Do you have any thoughts on who, currently on the world stage, this may be?
Various groups have falsely claimed to be Jews over the years. Today certain groups in the Church believe they’ve inherited the promises God made to Israel. Some of them even live according to to the Levitical system. This view is called Replacement Theology.
Some teach that the European Jews, who make up a majority of Israel’s citizenry today, are not a legitimate part of Israel because they are predominantly the descendants of converts and not true sons of Jacob. But the Bible disagrees with that view and in any case, you’ll find members of all 12 tribes in Israel today. The so-called 10 lost tribes were never completely lost. We know this because 2 chronicles 11:14-17 tells us at the time of the rebellion that divided the Kingdom the faithful from all 12 tribes moved to the south. And at the end of the Age God will find 12,000 each from 12 tribes in Israel to serve as His evangelists on Earth. (Rev. 7:1-8)
I think Paul gave a good answer to your question in Romans 2:28-29. He said,
“A person is not a Jew who is one only outwardly, nor is circumcision merely outward and physical. No, a person is a Jew who is one inwardly; and circumcision is circumcision of the heart, by the Spirit, not by the written code. Such a person’s praise is not from other people, but from God.”