From what i can understand the New Covenant promised to the house of Israel and to the house of Judah has not yet been fulfilled:
"Behold, the days come, saith the LORD, that I will make a new covenant with the house of Israel, and with the house of Judah: 32. Not according to the covenant that I made with their fathers in the day that I took them by the hand to bring them out of the land of Egypt; which my covenant they brake, although I was an husband unto them, saith the LORD: 33. But this shall be the covenant that I will make with the house of Israel; After those days, saith the LORD, I will put my law in their inward parts, and write it in their hearts; and will be their God, and they shall be my people. 34. And they shall teach no more every man his neighbour, and every man his brother, saying, Know the LORD: for they shall all know me, from the least of them unto the greatest of them, saith the LORD: for I will forgive their iniquity, and I will remember their sin no more" (Jer.31:31-34).
According to this the fathers of those who will make up the houses of Israel and Jacob will the the physical descendants of Israel because it was them who broke the covenant. Since their fathers are the physical descendants of Israel then they will also be the physical descendants of Israel.
When this prophecy will be fulfilled then all of the physical descendants of Israel who belong to both houses will know the Lord "from the least of them unto the greatest of them" and they will all have their sins forgiven and will all be saved.
This has never happened in the past so its fulfillment remains in the future.
Heb 8:6 But
now He has obtained a more excellent ministry, inasmuch as He is also Mediator of a better covenant, which was established on better promises.
(Present tense during the first century)
Heb 8:7 For if that first
covenant had been faultless, then no place would have been sought for a second.
Below we find the exact text from Jeremiah 31:31-34 copied word for word to show its fulfillment in verses 6 and 13 of this passage. In the NKJV the Old Testament text is in Uppercase letters.
Heb 8:8 Because finding fault with them, He says: "BEHOLD, THE DAYS ARE COMING, SAYS THE LORD, WHEN I WILL MAKE A NEW COVENANT WITH THE HOUSE OF ISRAEL AND WITH THE HOUSE OF JUDAH—
Heb 8:9 NOT ACCORDING TO THE COVENANT THAT I MADE WITH THEIR FATHERS IN THE DAY WHEN I TOOK THEM BY THE HAND TO LEAD THEM OUT OF THE LAND OF EGYPT; BECAUSE THEY DID NOT CONTINUE IN MY COVENANT, AND I DISREGARDED THEM, SAYS THE LORD.
Heb 8:10 FOR THIS IS THE COVENANT THAT I WILL MAKE WITH THE HOUSE OF ISRAEL AFTER THOSE DAYS, SAYS THE LORD: I WILL PUT MY LAWS IN THEIR MIND AND WRITE THEM ON THEIR HEARTS; AND I WILL BE THEIR GOD, AND THEY SHALL BE MY PEOPLE.
Heb 8:11 NONE OF THEM SHALL TEACH HIS NEIGHBOR, AND NONE HIS BROTHER, SAYING, 'KNOW THE LORD,' FOR ALL SHALL KNOW ME, FROM THE LEAST OF THEM TO THE GREATEST OF THEM.
Heb 8:12 FOR I WILL BE MERCIFUL TO THEIR UNRIGHTEOUSNESS, AND THEIR SINS AND THEIR LAWLESS DEEDS I WILL REMEMBER NO MORE."
Heb 8:13 In that He says,
"A NEW COVENANT," He has made the first obsolete. Now what is becoming obsolete and growing old is ready to vanish away.
(Present tense during the first century)
Heb 9:15 And for this reason
He is the Mediator of the new covenant, by means of death, for the redemption of the transgressions under the first covenant, that those who are called may receive the promise of the eternal inheritance.
(Present tense during the first century)
Heb 10:16 "
THIS IS THE COVENANT THAT I WILL MAKE WITH THEM AFTER THOSE DAYS, SAYS THE LORD: I WILL PUT MY LAWS INTO THEIR HEARTS, AND IN THEIR MINDS I WILL WRITE THEM,"
Heb 10:17 then He adds, "THEIR SINS AND THEIR LAWLESS DEEDS I WILL REMEMBER NO MORE."
Heb 10:18
Now where there is remission of these, there is no longer an offering for sin.
(Present tense during the first century)
Heb 12:18 For you have not come to the mountain that may be touched and that burned with fire, and to blackness and darkness and tempest,
Heb 12:19 and the sound of a trumpet and the voice of words, so that those who heard
it begged that the word should not be spoken to them anymore.
Heb 12:20 (For they could not endure what was commanded: "AND IF SO MUCH AS A BEAST TOUCHES THE MOUNTAIN, IT SHALL BE STONED OR SHOT WITH AN ARROW."
Heb 12:21 And so terrifying was the sight
that Moses said, "I AM EXCEEDINGLY AFRAID AND TREMBLING.")
In the passages below we have the New Covenant specifically applied to the Church.
Heb 12:22
But you have come to Mount Zion and to the city of the living God, the heavenly Jerusalem, to an innumerable company of angels,
Heb 12:23
to the general assembly and church of the firstborn who are registered in heaven, to God the Judge of all, to the spirits of just men made perfect,
Heb 12:24
to Jesus the Mediator of the new covenant, and to the blood of sprinkling that speaks better things than
that of Abel.
2Co 3:6
who also made us sufficient as ministers of the new covenant, not of the letter but of the Spirit; for the letter kills, but the Spirit gives life.
2Co 3:7 But if the ministry of death, written
and engraved on stones, was glorious, so that the children of Israel could not look steadily at the face of Moses because of the glory of his countenance, which
glory was passing away,
2Co 3:8 how will the ministry of the Spirit not be more glorious?
Mat 26:28
For this is My blood of the new covenant, which is shed for many for the remission of sins.
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