Key Greek words used in biblical texts that decide the meaning of the text.

The seed of Abraham

Genesis 12:1-3:
"Now the LORD had said unto Abram, Get thee out of thy country, and from thy kindred, and from thy father’s house, unto a land that I will shew thee:

And I will make of thee a great nation, and I will bless thee, and make thy name great; and thou shalt be a blessing: And I will bless them that bless thee, and curse him that curseth thee: and in thee shall all families of the earth be blessed." 

"For as in Adam all die, even so in Christ all will be made alive." 
-- 1 Corinthians 15;22

The apostle Paul said:
"Now the promises were spoken to Abraham and to his descendant. Scripture does not say, "and to the descendants," referring to many, but "and to your descendant," referring to one, who is Christ." (Galatians 3:16).

The above promise in Genesis 12:2-3 was the very first promise that God made to Abraham, and this promise therefore forms the basis for: 

(a) Any subsequent promise that God made to Abraham; and 

(b) Anything that God later did in the life of Abraham and his descendants.

Seed of Abraham

The second time God made a promise to Abraham, He said,

Genesis 17:3-6
"And Abram fell on his face. And God talked with him, saying, As for Me, behold! My covenant is with you, and you shall be a father of a multitude of gôyim (Gentiles/Gentile nations). Neither shall your name any more be called Abram, but your name shall be Abraham. For I have made you a father of a multitude of gôyim, and I will make you exceedingly fruitful, greatly so, and I will make gôyim  (Gentiles/Gentile nations) of you, and kings shall come out of you.". *

[ Strongs Hebrew Dictionary H01471: gôy ] 
Apparently from the same root as H1465 (in the sense of massing); a foreign nation; hence a Gentile; also (figuratively) a troop of {animals} or a flight of locusts: - {Gentile} {heathen} {nation} people.

* Notice how God repeated the above promise (Genesis 17:3-6) three times. 

HOW IT CAME ABOUT THAT THE PROMISE WAS FULFILLED

OUT OF ONE NATION, A MULTITUDE OF NATIONS:-

Abraham 

fathered a son named 

Isaac, 

who fathered a son named 

Jacob/Israel, 

who became the father of 

Twelve sons, 

one of whom was named Judah, patriarch of the tribe of Judah or "the Jews", the tribe, through whom God chose to bring the seed promised to Abraham (Jesus) into the world, the promised Messiah through Whom "all the families of the earth are blessed" (Jesus was born a Jew).

In Genesis we read that when Jacob was announcing blessing upon his grandsons, Joseph "saw that his father Jacob (Israel) placed his right hand on (Joseph's youngest son's) Ephraim's head, it displeased him. So he took his father's hand to move it from Ephraim's head to Manasseh's head.
  
Joseph said to his father, "Not so, my father, for this is the firstborn. Put your right hand on his head", but his father refused and said, "I know, my son, I know. He (Manasseh) too will become a nation and he too will become great. 

In spite of this, his younger brother (Ephraim) will be even greater and his descendants will become [the fullness of the Gentiles]* a multitude of nations."

* [ Hebrew, m'lo gôy: (the) fulnness (of the) Gentile (nations) ]. (Genesis 48:17-19).

Hundreds of years later the prophet Isaiah prophesied:  

"Ephraim shall be broken so that it shall not be a people." -- Isaiah 7:8

Israel - the twelve tribes descended from Jacob/Israel's twelve sons - split into two kingdoms after the time of king Solomon: The northern kingdom of Israel, and the southern kingdom of Judah. The Northern kingdom's tribes collectively became known as "Ephraim" (the dominant tribe among them):

THE NORTHERN KINGDOM, 
A.K.A "THE HOUSE OF ISRAEL",
A.K.A "EPHRAIM"

The tribe of Reuben. 
The tribe of Gad.
The tribe of Asher.
The tribe of Naphtali.
The tribe of Dan (substituted with Manasseh in Revelation chapter 7).
The tribe of Simeon.
The tribe of Levi.
The tribe of Issachar .
The tribe of Zebulun.
The tribe of Joseph.

Ephraim, son of Joseph, was born in Egypt to an Egyptian mother, and Jacob/Israel prophesied that Ephraim's descendants would become "the fullness of the Gentiles" (or "a multitude of nations").  

Manasseh, son of Joseph, was also a Gentile born in Egypt to an Egyptian mother.

THE SOUTHERN KINGDOM
A.K.A "THE HOUSE OF JUDAH"

* The tribe of Benjamin - Patriarch, Benjamin, son of Jacob (Benjamin was not "Jewish").
* The tribe of Judah ("the Jews") - Judah being the ancestor of king David, the ancestor of Jesus the Messiah, according to the flesh (through his mother).
There were also Levitical priests serving in the Temple.

WHAT HAPPENED HISTORICALLY TO THE HOUSE OF ISRAEL?

Hosea 1:6b-11a (the prophet, writing about the house of Israel, a.k.a Ephraim: 

"For I will no more have mercy on the house of Israel. But I will utterly take them away .."  

The prophet, writing about the house of Judah: 

".. But I will have mercy on the house of Judah, and will save them by the LORD their God, and will not save them by bow, nor by sword, nor by battle, by horses, nor by horsemen."

In circa 722 BC, the Northern kingdom's tribes, who had collectively become known as "Ephraim" (the dominant tribe among them) were judged by God because of their idolatry: 

The kingdom was attacked and defeated by the Assyrian king, and the vast majority were exiled from the land (the Northern kingdom). 

They became  scattered among the nations. Yet this is what Hosea prophesied about them:   

Hosea 1:6b-11a:

   "Now when she had weaned Loruhamah, she conceived, and bare a son. Then said God, Call his name Loammi: for all of you are not my people, and I will not be your God. 

   Yet the number of the children of Israel shall be as the sand of the sea, which cannot be measured nor numbered; and it shall come to pass, that in the place where it was said unto them, All of you are not my people, there it shall be said unto them, All of you are the sons of the living God. 

   Then shall the children of Judah and the children of Israel be gathered together, and appoint themselves one head."

The last sentence (and how it either has been, or will be fulfilled) is the subject of a great deal of debate among Christians and wherever there are two Christians, there are three opinions about it, but it's important to take note of the fact that although there was a small remnant of the house of Israel/Ephraim that escaped to Judah when the Northern kingdom's people became exiled, the above prophecy is not referring to them: 

The house of Israel ceased being a nation circa 722 B.C. They are no longer one nation:

From circa 722 BC, and following their exile after the invasion of the Northern kingdom by the king of Assyria (which resulted in the ending of the Northern kingdom), the house of Israel became scattered among the nations.

The descendants of the 10 tribes of the house of Israel have intermarried with the Gentiles in the nations since their 8th century BC dispersion, to the point where over time "the lost ten tribes" are untraceable today:

"Ephraim shall be broken so that it shall not be a people." -- Isaiah 7:8

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By the time the apostle Paul made the following statement, the seed of Ephraim/the house of Israel had become mixed with the seed of the Gentiles:

"What if God, willing to show his wrath, and to make his power known, endured with much longsuffering the vessels of wrath fitted to destruction: And that he might make known the riches of his glory on the vessels of mercy, which he had before prepared unto glory,

Even us, whom he has called, not of the Jews only, but also of the Gentiles? As he says also in Hosea, 

'I will call them my people, which were not my people; and her beloved, which was not beloved. And it shall come to pass, that in the place where it was said unto them, All of you are not my people; there shall they be called the children of the living God.' " (Romans 9:22-26).

Right there Paul included Gentiles who believe in Jesus in a prophecy that in its context in Hosea speaks only of the house of Israel/Ephraim.

"I know, my son, I know. 
He (Manasseh) too will become a nation 
and he too will become great. 
In spite of this, his younger brother (Ephraim) will be even greater 
and his descendants will become [the fullness of the Gentiles]* 
(Genesis 48:17-19)

* a multitude of nations." [ Hebrew, m'lo gôy: (the) fulnness (of the) Gentile (nations) ]. 

So Paul says: 

Romans 4:16-17
"Therefore it is of faith so that it might be according to grace; for the promise to be made sure to all the seed, not only to that which is of the Law, but to that also which is of the faith of Abraham, who is the father of us all (as it has been written, "I have made you a father of many nations") --before God, whom he believed, who makes the dead live, and calls the things which do not exist as though they do exist."

Colossians 3:11
"There is neither Greek nor Jew, circumcision and uncircumcision, foreigner, Scythian, slave or freeman, but Christ is all things in all."

"And Abram fell on his face. And God talked with him, saying, 
As for Me, behold! My covenant is with you, 
and you shall be a father of a multitude of gôyim (Gentiles/Gentile nations). 
Neither shall your name any more be called Abram, 
but your name shall be Abraham. 
For I have made you a father of a multitude of gôyim, 
and I will make you exceedingly fruitful, greatly so, 
and I will make gôyim  (Gentiles/Gentile nations) of you, 
and kings shall come out of you.".
(Genesis 17:3-6)

The evidence for the key role played by the natural descendants of Abraham, Isaac and Jacob lies in:

(i) The history of Israel; and 

(ii) The existence of both the Old and New Testament scriptures (64 of the 66 books contained in the Protestant Canon were written by "the Jews"); and

(iii) The existence of Gentile Christians and Christian assemblies all around the world (because the first of all of them were founded by Jews);

and their key role is laid out by Paul in Romans 9:3-6, and hidden in the metaphoric symbolism of the sun and moon and eleven stars seen by Joseph in a dream (Joseph was the 12th of twelve stars) in Genesis 37:9, which is also found in Revelation 12:1.

The evidence for the key role played by Gentile Christians lies in the spread of the gospel to the four corners of the earth, which Christ, the promised seed of Abraham, mentioned when He said,

"This gospel of the kingdom shall be preached in all the world for a witness unto all nations; and then shall the end (of the age) come." (Matthew 24:14). 

But the central and crucial role is that which is played by Christ, the seed of Abraham, Himself. Were it not for our God and Savior Jesus Christ, there would not be any role for anyone else to play, or to have played.

In Hosea 1:11a, and in the same prophecy uttered by a few other prophets, God promised that He will gather the house of Israel and the house of Judah back into the land He gave to their fathers and make them one nation in the land, but it is God Himself who will do this, and not before the time Christ makes all (created) things new because nothing happens without the Messiah's involvement, i.e it will be the actions of the son of David, the Son of God, after returning as King of kings and Lord of lords. 

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