Heb 8 is not discussing the Old Testament, it is discussing the Old Covenant.
Interesting on a thread about the importance of words, so many are sloppy Bible readers.
A Covenant isn't a Testament.
That the Gentiles would be saved was never a mystery, it will happen during the Tribulation period.
The rebuilding of David's tabernacle refers to the Millennium period, not the church age.
You will note in vs14 'at first' and then in vs 16 'after this', there are two callings for the Gentiles, one during the Church age and one 'after this' during the Trib. period.
What is unique about the mystery of the Church, is that both Jew and Gentile are one Body, neither Jew nor Gentile.
The Council was explaining that Gentiles were always intended to be saved, but there are two callings of them for two different ages.
I wish that were true.
But there are so many threads that run a line from Israel to the church that no reasonable reader, even reading at genius levels of efficiency and accuracy, could be expected to ignore the obvious application of these passages to the contemporaneous church.
Look again at how James used the passage he quoted from Amos. In context, at the first must be associated with the report of Peter, how God poured out His Holy Spirit on the house of Cornelius after Peter obeyed the heavenly vision, and offered such as proof to the Jerusalem church that God meant for the Gentiles to be included in the Church Christ was building at that very moment in time.
But Amos was a prophecy spoken of the fall and ruination of Israel and the House of David, for their grievous sins against God. The only temporal aspect of the After this of Acts 15:16 that we can be sure of is that the rebuilding of the House of David comes sometime after the punishment had been executed. And it can hardly be argued that at the time of Christ, the division of the kingdom, the dispersion of the Jews, and the extreme humbling of the line of David was already long underway, so the rebuilding spoken of by Amos could easily be coordinate in time with the first appearance of Christ.
And how better to restore the line of David to the full measure of glory than by the appearance of the Christ? It is in this context that James applies that passage, not to some second future calling of the Gentiles, but to the truth God is right then and there impressing on the Jewish believers, that Gods Gospel of Christ must be for everyone, including Gentiles. Indeed, the Greek word used here for build up is based on the same verb Jesus uses in Matthew 16:18, oikodomeō, when he says he will build his church.
In short, reading two callings of Gentiles into this is an impossible stretch, at least for me, and by no means a required reading of the text. They are one and the same calling.
Honestly, I understand how it is being a dispensationalist, how everything has to be force-fitted to the separate destinies paradigm, no matter how flimsy the evidence. And you can get so good at it that you can get to where you dont understand why not everyone sees it as easily as you do. I get that.
But I can no longer go there, because I have to be honest with myself first of all, and I would be kidding myself to pretend I believed that James here just jumps out of the immediate context and weirdly pulls in some reference to the distant future, when the simpler understanding is that He took Amos to be speaking of what was happening then and there, and thats why he used the text as he did, to validate the contemporaneous acceptance of Gentiles as full, Spirit-filled members of Gods church.
As for covenant versus testament, you make bald assertions that they are unrelated terms, yet you offer no proof, other than, apparently, a perceived differentiation that is really a product of modern English and not of Biblical word study. BTW, do you happen to be a King-James Onlyist? Im only curious because that could explain why you are camping so hard on a distinction that exists mainly in modern English. But I assure you, the two terms can be used interchangeably in most cases, and that the naming of our Scriptures into Old and New Testaments was intended to correspond to the Old and New Covenants.
The word in question is diathēkē, which is variously translatable as either will or covenant, because, as I said at the first, the two concepts overlap with each other. It is as artificial and misleading to overlook the similarities as it is to overlook the differences. Testament, BTW, is just Latin for covenant.
Picking up that a will is being discussed is a matter of context. As I said before, a will is just a promise made that is to be kept after the death of the promisor. But it is still primarily a promise, the setting forth of an obligation between two parties, i.e., a covenant. Indeed, most wills are written as impliedly between two or more living parties, the testator(s) and the beneficiaries, with the intent for the obligations of the promise to kick in after the death of one or more of the testators, just as Hebrews 9 teaches. I am an attorney. I write these things. This is what they are. I am sorry if that disappoints you, but what can I do? I dont make the rules.
Here are some passages variously translated in the KJV as covenant or testament. They all use diathēkē:
Mat 26:28 For this is my blood of the new testament, which is shed for many for the remission of sins.
Heb 8:6 But now hath he obtained a more excellent ministry, by how much also he is the mediator of a better covenant, which was established upon better promises.
Heb 8:8 For finding fault with them, he saith, Behold, the days come, saith the Lord, when I will make a new covenant with the house of Israel and with the house of Judah:
2Cor 3:5-6 Not that we are sufficient of ourselves to think any thing as of ourselves; but our sufficiency is of God; [6] Who also hath made us able ministers of the new testament; not of the letter, but of the spirit: for the letter killeth, but the spirit giveth life.
Note in the Corinthian passage that Paul uses the term diathēkē of his contemporaneous ministry of the Gospel of Christ. Again, remember, testamentum is just Latin for covenant. So unless you are relying on the KJV to supply inspired information not present in the Greek, there is no deep dark mystery here. Testament is covenant, generally speaking.
But knowing how these things go, and having been a devoted dispensationalist myself at one point, I ask you to consider yet another passage:
Exodus 19:6 "And you shall be to Me a kingdom of priests and a holy nation.' These are the words which you shall speak to the children of Israel."
There can be no doubt God is here speaking as the Covenanting God, who has acted to secure a people for himself, and who in the very next chapter will lay down the law, literally, that is to govern the Covenant.
And yet we see Peter, who has received a vision of the Gentiles being welcomed into the church, has seen the Holy Spirit poured out on those Gentiles, has been rebuked by Paul for treating Gentiles in the church as if they were obliged to keep the Old Covenant, using this exact passage, the covenant declaration of God claiming a people for Himself, in reference to contemporaneous Christians:
1 Peter 2:9 "But you are a chosen generation, a royal priesthood, a holy nation, His own special people, that you may proclaim the praises of Him who called you out of darkness into His marvelous light;"
God spoke it to Israel, yet Peter attaches it to the church. It is an amazing thing to be loved of God, is it not?
Peace,
SR