And gentiles never became Israelites. Ever.
You two were talking about Ruth. Wasn't she a gentile (a Moabite) who married an Israelite and became the great-grandmother of King David? Prior to that, Joseph married an Egyptian woman (
Gen 41:45), so Ephraim and Menasseh were also mixed, and that double tribe became the biggest of Israel. Also, recall that approx. 215 years after Joseph a
"mixed" multitude left Egypt with the descendants of Jacob.
Exodus 12:37
The Israelites journeyed from Rameses to Succoth with about 600,000 men on foot, besides women and children. And a mixed multitude also went up with them, along with great droves of livestock, both flocks and herds.
The Hebrew word translated to "mixed" in this passage is "arab". So everyone who left Egypt - the descendants of Jacob and the "arab" multitude - entered into the same marriage covenant with The Almighty to become one people:
Deuteronomy 29:10-29 (but only snipped up to verse 12)
All of you are standing today in the presence of the Lord your God—your leaders and chief men, your elders and officials, and all the other men of Israel, together with your children and your wives, and the foreigners living in your camps who chop your wood and carry your water.
12 You are standing here in order to enter into a covenant with the Lord your God, a covenant the Lord is making with you this day and sealing with an oath,
The passage continues by saying even all of their children will be held to the same covenant. The Almighty said there will be one law that all are to follow in the kingdom of Israel regardless of previous background:
Exodus 12:49
One law shall be for the native-born and for the stranger who dwells among you
This was the template; the example that would be fulfilled through Messiah.
Fast-forward to Paul and he explains that very mystery of God that was hidden for centuries until the Messiah's work: "Christ in you"; that Gentiles could attain salvation. How? God has only known Israel of all the nations (
Amos 3:2). Every principality received a nation and Israel was The Living God's possession (
Deuteronomy 32:8).
The Almighty is still the same. His ways are explained through the examples of ancient Israel (
1 Corinthians 10:11). Notice how on a smaller scale out of all the tribes of Israel, He made one tribe - the Levites - His "personal possession". So likewise, out of all nations on earth, one nation - Israel - is His. Salvation is for Israel. As Messiah said, "
salvation is of the Jews" (
John 4:22).
He only knows Israel. But it's also true that "God so loves the world" (
John 3:16) and calls all men to repent (
Acts 17:30). So in order to
save the world He made a way for those
in the world to join Israel through His Son (Who is the Root of the tree of Israel -
Romans 11:16-18), because salvation is for Israel as Messiah said (
John 4:22).
So through Israel's punishment (their scattering), He has sown Israel into the world;
casting them among the Gentiles (
Jeremiah 31:27) to bless the Gentiles while bringing in the full number of them into Christ (
Romans 11). When the full number of Gentiles comes in He will draw the natural branches back to Him,
closing the net. "
The kingdom of Heaven is like a fishing net bringing in all types of fish" (
Matthew 13:47).
Acts 1:6-7
When they therefore were come together, they asked of him, saying, Lord, wilt thou at this time restore again the kingdom to Israel?
7 And he said unto them, It is not for you to know the times or the seasons, which the Father hath put in his own power.
Messiah never told them it wouldn't happen. He said the
timing of when the kingdom would be restored wasn't for them to know. For Gentiles whom He foresaw would love Him, He made a way for them to join His people because Israel is God's possession. Jerusalem is Messiah's bride.
The Messiah isn't coming back for a religion. He's coming back for a people. The "Kingdom of God" is the Kingdom of Israel because God is Israel's King (this has been true since the beginning before the people wanted to be like other nations -
1 Samuel 8:7), which will be headquartered in Jerusalem with Messiah as her king. The City of Light. And we will all be there as citizens: believing Jew and believing Gentile, while no one else will be allowed in, not the unbelieving Jew or the unbelieving Gentile.
We will all be one people.