In chapter 15, Peter, the prophet of the Lord, stands up and reveals the will of the Lord in the matter and it was declared to be scripture.
Citation, please? I don't see anything in Acts 15 where anything is 'declared to be scripture', and what St. Peter says which is received by the assembly is a short exposition concerning the equality between the Jewish and the Gentile converts (verses 7-11). Then St. Paul and Barnabas speak concerning the miracles worked among the Gentiles (verse 12), and then, as I wrote already, St. James speaks of the decision of the assembly in this matter (verses 13-21), with a long quotation from Amos before giving the judgment,
in his own words and
in first person ("Therefore I judge that we should not trouble those from among the Gentiles..."), to be followed by a letter composed by all of them to be given for the instruction of the brothers among the Gentiles in Antioch, Syria, and Cilicia (verses 23-29).
This is of course elaborating on the revelation God gave him in chapter 10: God spoke, prophet delivered His words, disciples followed.
Yes, of course, because the entire point of both is that there ought not be this division between Jew and Gentile in the Church. We're not in disagreement about that; my point is that the Councils which you reject by virtue of them being examples to you of "following men" follow the same pattern of the Council of Jerusalem which you presumably accept, as it is found in Bible itself.
Whom was the prophet to speak the will of the Lord through revelation in the the Eumerical Councils?
Is St. James a prophet because he spoke for the assembly at Jerusalem? In that case, we can say that of any of the bishops who presided over the various councils and synods in that same role: HH St. Alexander of Alexandria at Nicaea, the several who presided over the various sessions of Consantinople I (HH St. Timothy of Alexandria, St. Gregory Nazianzus, etc.), etc. That is not my position, however. For one thing, you immediately then run into problems when you consider that Meletios of Antioch presided at Constantinople I, but the same Meletios was opposed by HH St. Athanasius the Apostolic for elsewhere having condemned the Orthodox (Nicene) Patriarch of Antioch HH Eustathios at the synod of Melitene for confessing that Christ was homoousios with the Father, as is necessary to uphold the faith of the Church. For another thing, having spoken and quoted scripture, as St. James did, is not what put him in the position that he had at the Council. It was rather a matter of him being the local bishop that he would declare the ruling of the assembly. That was my point in pointing out that ~120 years later, the same happened with regard to HG Apollinarius, who presided over the synod at Heirapolis which was in Phrygia, as the Montanists were likewise Phrygians who had come out of his local diocese/area. So it's the same pattern that we see in the Bible also practiced well after the Council described in Acts 15.
Where in scripture may I read their words given by the Lord?
First of all, don't think I'm not seeing what you are doing here: We are talking about what is found in the Acts of the Apostles, which is already scripture, so the standard to which you are holding the later fathersis one that is already 'pre-met' due to the fact that scripture is what we're talking about (so it makes your position look stronger than it is because you are 'arguing from scripture', whereas I am 'arguing from the words of sinful men' or whatever dumb nonsense non-point there is in maintaining this anachronistic pseudo-division). This is why I already pointed out that James argued
in his own words in verses 18-21, wherein he pronounces the judgment of the Council to be related via epistle a few verses later. The fact that they are his own words and not a verbatim quote from previously accepted scriptures (as his earlier quote from Amos is) is irrelevant, of course, as both are scripture. The question I would have then is: What if they weren't? I say this because of course
at the time, it was simply the ruling that St. James was giving, in accordance with the mind of the Church as arrived at in council.
That was the point of meeting in council in the first place. Because in so far as any one man is concerned (James, Peter, Paul, Barnabas, etc.), they are dealing in real time with the problem before them, and with recourse to the teachings they have been given both presently (from our Lord Jesus Christ within every man's recorded memory, and through their fellow apostles) and through the deposit left by their own fathers (in the Old Testament).
This is the exact same situation that there is in any subsequent later Council or Synod, down to this very day, hence my question regarding when something which is clearly acceptable becomes unacceptable, and by what measure. If it's the same situation, and the same methodology, and the same everything, then there is no basis by which to say that anyone ever went astray, at least not according to the same metric by which we find Jerusalem acceptable. You must instead invent some other artificial division whereby what was acceptable in 50 AD is suddenly unacceptable in 144 AD or 177 AD or whenever, and you must show
why it is so, if all else has remained constant (read: if they're not doing anything appreciably different at Antioch in 160 than they did at Jerusalem in 50).
Requiring that anyone presiding at a council be a prophet is merely an attempt to force Mormon epistemology on the Church, and since I bet we wouldn't agree on that anyway (after all, none of the men you call your 'living prophets' today are recognized as such by any Christian tradition), it is useless to waste anyone's time discussing it. However, your question regarding where their words are so that you may read them in scripture is easy enough to answer by looking at the surviving acts of the various councils, which are preserved in various places should you wish to study them as actual history and not to buttress Mormon theories about what must've happened at said councils vis-a-vis the 'Great Apostasy' theory.
For instance, HH St. Cyril's Epistle to Nestorius forms part of the Acts of the Council of Ephesus (431), preserved under the Latin title "Cum Salvator Noster" at the Catholic Encyclopedia (not a source I am actually all that fond of, as its Roman Chalcedonian bias is palpable, but which is nevertheless a good repository of English translations of such things, if you cannot find them elsewhere). Quoting it here would be a bit daunting (it is many, many paragraphs long, and should really be read
in its entirety), but what is handy about that particular website is that it places quotations from scripture in italics, so we can see that in introductory paragraph alone, which is only six total sentences, there are three such direct quotations woven into the text. The rest of the letter continues in a similar mode.
It has been said, though I cannot remember by whom exactly, that if the Bible were lost to us somehow, we would be able to reconstruct it from direct quotations in the fathers alone. Not all of these were given in councils, but some were (as in the above example), and at any rate there is no division between an epistle like
Cum Salvator Noster and one of St. Cyril's other writings, such as
That Christ is One, his commentary on the Gospel of St. John, or
Against Julian the Apostate.