the NT does not get its authority from the OT because as far as we know the OT does not reference the NT anywhere. not one single mention. there are prophecies about jesus and other events in the OT but it does not reference the NT writings
Well, if there are prophecies concerning Jesus in the Old Testament, then how exactly does it not get it's fulfillment in the New Testament writings? The point is, the Old Testament points to Christ. Consider passages like these:
'The Lord thy God will raise up unto thee a Prophet from the midst of thee, of thy brethren, like unto me; unto him ye shall hearken;
According to all that thou desiredst of the Lord thy God in Horeb in the day of the assembly, saying, Let me not hear again the voice of the Lord my God, neither let me see this great fire any more, that I die not.
And the Lord said unto me, They have well spoken that which they have spoken.
I will raise them up a Prophet from among their brethren, like unto thee, and will put my words in his mouth; and he shall speak unto them all that I shall command him.
And it shall come to pass, that whosoever will not hearken unto my words which he shall speak in my name, I will require it of him.
Dueteronomy 18: 15-19
Consider what Jesus said in the New Testament:
'I am come a light into the world, that whosoever believeth on me should not abide in darkness.
And if any man hear my words, and believe not, I judge him not: for I came not to judge the world, but to save the world.
He that rejecteth me, and receiveth not my words, hath one that judgeth him: the word that I have spoken, the same shall judge him in the last day.
For I have not spoken of myself; but the Father which sent me, he gave me a commandment, what I should say, and what I should speak.
And I know that his commandment is life everlasting: whatsoever I speak therefore, even as the Father said unto me, so I speak
.' St John 12: 46-50
What about Isaiah 53?
Who hath believed our report? and to whom is the arm of the LORD revealed?
2For he shall grow up before him as a tender plant, and as a root out of a dry ground: he hath no form nor comeliness; and when we shall see him, there is no beauty that we should desire him.
3He is despised and rejected of men; a man of sorrows, and acquainted with grief: and we hid as it were our faces from him; he was despised, and we esteemed him not.
4Surely he hath borne our griefs, and carried our sorrows: yet we did esteem him stricken, smitten of God, and afflicted.
5But he was wounded for our transgressions, he was bruised for our iniquities: the chastisement of our peace was upon him; and with his stripes we are healed.
6All we like sheep have gone astray; we have turned every one to his own way; and the LORD hath laid on him the iniquity of us all.
7He was oppressed, and he was afflicted, yet he opened not his mouth: he is brought as a lamb to the slaughter, and as a sheep before her shearers is dumb, so he openeth not his mouth.
8He was taken from prison and from judgment: and who shall declare his generation? for he was cut off out of the land of the living: for the transgression of my people was he stricken.
9And he made his grave with the wicked, and with the rich in his death; because he had done no violence, neither was any deceit in his mouth.
10Yet it pleased the LORD to bruise him; he hath put him to grief: when thou shalt make his soul an offering for sin, he shall see his seed, he shall prolong his days, and the pleasure of the LORD shall prosper in his hand.
11He shall see of the travail of his soul, and shall be satisfied: by his knowledge shall my righteous servant justify many; for he shall bear their iniquities.
12Therefore will I divide him a portion with the great, and he shall divide the spoil with the strong; because he hath poured out his soul unto death: and he was numbered with the transgressors; and he bare the sin of many, and made intercession for the transgressors
A clear cut demonstration of what the Messiah would have to do. And all this is in the Old Testament.
Here's what we find in the book of Daniel:
'I saw in the night visions, and, behold, one like the Son of Man came with the clouds of heaven, and came to the Ancient of Days, and they brought him near before him.
And there was given him dominion, and glory, and a kingdom, that all people, nations, and languages, should serve him: his dominion is an everlasting dominion, which shall not pass away, and his kingdom that which shall not be destroyed.' Daniel 7: 13-14.
How many times in the Gospels did Jesus refer to himself as the Son of Man?
there are prophecies in the NT that are found in the OT. Just because a collection of writings, in some places, mention OT prophecies does not mean that the collection of writings are inspired or that they are somehow linked to the OT.
Well, you can't separate the Old and New Testaments. Jesus fulfilled countless prophecies in the Old Testament, prophecies in the Psalms, books of Moses, and the books of the prophets. As I said, and as I have shown, the New Testament gets its authority from the Old.
And just to add, the church already was on a consensus of what was inspired scripture before any council took place, meaning, the texts that were known to be inspired were already circulated among the churches.