Let’s jump to the NT where it specifically says. Ro 1:16 I am not ashamed of the gospel, because it is the power of God for the salvation of everyone who believes:first for the Jew, then for the Gentile
1. Let the bible identify the ancestry of Paul's mostly 'gentile' Roman congregation:
Rom 4:1 But if so, what can we say about Abraham, our forefather by natural descent?
Rom 4:16 That is why all turns upon faith; it is to make the promise a matter of favour, to make it secure for all the offspring, not simply for those who are adherents of the Law but also for those who share the faith of Abraham — of Abraham who is the father of us all
These passages, especially vs 1, eliminates any argument of a "spiritual Israel". Although there is now a spiritual element to NT Israel, it is only made with the physical descendants of Jacob, as the scriptures proclaim.
I can even prove with a degree of certainty from historical and biblical evidence, Cornelius, the first "gentile" convert, was also a physical descendant of Jacob.
Gal 3:28 There is neitherJew nor Greek, slave nor free, male nor female, for you are all one in Christ Jesus.
2. The term “Greek” in vs 28 is “hellene-G1672”. It is translated “gentiles” in other passages. But its more accurate definition is someone who speaks Greek. Strong’s extends the definition to a non-Israelite, which is partially correct, but it can also apply to a Greek speaking Israelite.
It is common knowledge most Jews (house of Judah) residing in areas outside of Judah, i.e.., Galatia, etc., were “hellenes”. Not because they 'were' of Greek descent, but because they 'spoke' Greek. This does not make the Jews in Galatia non-Israelite. The language one speaks or place of residence does not necessarily dictate their ancestral origin. Notice:
Joh 7:35 Then the Jews said among themselves, "Where does He intend to go that we shall not find Him? Does He intend to go to the Dispersion among the Greeks and teach the Greeks?
Who are these Greek speakers that the Jews are claiming are dispersed among the Greek speakers? It certainly doesn't make much sense for Jesus to go to the dispersion among the Greek speakers to teach the Greek speakers. This connotes the "dispersion" is identifying a particular dispersed group among the Greek speakers. So who is this group dispersed among the Greek speakers in Galatia?
1Pe 1:1 Peter, an apostle of Jesus Christ, To the pilgrims of the Dispersion in Pontus, Galatia, Cappadocia, Asia, and Bithynia,
You read in the last point how the house of Israel (10 tribes) were dispersed throughout the gentiles, who by this time, were in Galatia speaking Greek. Peter was not only sent to the Jews but also the Israelites of the house of Israel. 1Pe 4:3 also provides evidence Peter’s audience in his first epistle were not exclusively Jewish:
It is quite enough to have done as pagans choose to do, during the time gone by! You used to lead lives of sensuality, lust, carousing, revelry, dissipation and illicit idolatry, (Moffatt)
Peter refers to the fact that some of his Greek speaking congregation from Galatia once lived as idolaters. Jewish congregants would not have led a life of idolatry, but the Greek speaking dispersed descendants of Jacob who lost their identity would have!!
Now, if we go the OT we can read goy, plural goyim, nation, people sometimes referring to the nation of Israel but that doesn’t mean they, the Israelites, were part of the Gentile nations.
3. But it does mean they can also be referred to as ‘gentiles’:
“And the LORD said unto her, two nations [Hebrew “goyim” = GENTILES] [are] in thy womb, and two manner of people shall be separated from thy bowels; and [the one] people shall be stronger than [the other] people; and the elder shall serve the younger.” (Gen 25:23 AV)
Notice how both Jacob and Esau are called 'goyim, elsewhere translated ‘gentiles’. This means Israelites as well as non-Israelites can be considered gentiles [nations] in the OT. Context would have to be considered to properly identify the intended group. There lies the confusion. The confusion spills over into the NT:
IOW, In the NT is says explicitly who the Gentiles are and they are not the Jews.
4. But they can be, depending on the context:
Joh 18:35 Pilate answered, "Am I a Jew? Your own nation [ethnos] G1484 and the chief priests have delivered You to me. What have You done?"
Here we have Pilate replying to Christ. In this case, the term “ethnos”-- translated many times as “gentiles” elsewhere in the New Testament-- were not Greeks or Romans but the Jews from the two tribes of the
house of Judah! The translators realized this and inserted the term “nation”.
The translators inserted their misconceptions on who they thought the Jews were by inserting “gentiles” for “ethnos”, when they “perceived” the context was referring to non-Jews, and “nation” was inserted when they “thought” it was speaking of Jews.
Not realizing the gentiles in the NT were mostly dispersed members from the 10 tribes (aka Ephraim) of the
house of Israel whom God had also made recipients of the covenant
(Heb 8:8-10), but were scattered among the ‘gentiles’[ethnos] (see verses in the last part of point 2
here) and had actually become unwitting ‘gentiles’ just like I was! This has led to a grave misidentification of New Covenant Christians.