How The Bible Itself Tells Us The Canon

 Many Catholics and Orthodox assert that unless we accept the Orthodox/Catholic traditions, we cannot know the canon. However, we see the Bible itself give us major evidences for the canon.

Jude the Apostle

1: Jude quotes 2 Peter as authoritative

Jude 1:17-18:  But you, beloved, remember the words which were spoken before by the apostles of our Lord Jesus Christ: how they told you that there would be mockers in the last time who would walk according to their own ungodly lusts.

Now, Jude is quoting the oral words of the apostles (plural), however he appears to take the wording from 2 Peter 3:3 which states:
Most importantly, you must understand that in the last days scoffers will come, scoffing and following their own evil desires.

Thus Jude is making chiefly reference to 2 Peter, yet also secondarily references what the other apostles said orally.

2: 2 Peter quotes Paul as authoritative

2 Peter 3:16, KJV: As also in all his epistles, speaking in them of these things; in which are some things hard to be understood, which they that are unlearned and unstable wrest, as they do also the other scriptures, unto their own destruction.

It is beyond clear that Paul's writings were seen as canonical early on, and having inspiration from God.

3: Paul claims to be inspired 

2 Thessalonians 3:14, KJV: And if any man obey not our word by this epistle, note that man, and have no company with him, that he may be ashamed.

4: Paul claims that Luke is inspired

Paul the apostle quoted the gospel of Luke as being equal to scripture:

1 Timothy 5:18

18 For the scripture saith, thou shalt not muzzle the ox that treadeth out the corn. And, The labourer is worthy of his reward.

Luke 10:7

7 And in the same house remain, eating and drinking such things as they give: for the labourer is worthy of his hire. Go not from house to house.

Comparing the Greek:

1 Timothy 5:18: Λέγει γὰρ ἡ γραφή, Βοῦν ἀλοῶντα οὐ φιμώσεις· καί, Ἄξιος ὁ ἐργάτης τοῦ μισθοῦ αὐτοῦ.

Luke 10:7: Ἐν αὐτῇ δὲ τῇ οἰκίᾳ μένετε, ἐσθίοντες καὶ πίνοντες τὰ παρ’ αὐτῶν· ἄξιος γὰρ ὁ ἐργάτης τοῦ μισθοῦ αὐτοῦ ἐστίν. Μὴ μεταβαίνετε ἐξ οἰκίας εἰς οἰκίαν.

The only difference is the word "gar", which translates to the English term "for". 

If the gospel of Luke is inspired, it should also be implied that Acts (written by the same author for a similar purpose) is inspired.

5: Luke extensively uses Mark and Matthew.

Since we now know that Luke is inspired, the usage of Mark and Matthew are also something to consider, the Spirit certainly saw the two as true if Luke used them. Additionally, there exists internal and external evidence that Mark and Matthew were the authors, which together makes for a case that they too are inspired.

6: Jesus claims the Old Testament to be inspired

Jesus claims that the Old Testament is inspired in the book of Luke in multiple places, quoting it with full authority. Jesus confirms that the Rabbinic canon of the Old Testament was correct: "Luke 24:44, KJV: And he said unto them, These are the words which I spake unto you, while I was yet with you, that all things must be fulfilled, which were written in the law of Moses, and in the prophets, and in the psalms, concerning me."

Here, Jesus affirms the threefold canon of the Jews, who divided the Old Testament into three categories, the law, the prophets and the writings. Now, Jesus used the word "psalms" for the entirety of the writings due to being the most significant book in the category. 

7: Paul claimed the Jewish canon of the Old Testament to be inspired

Romans 3:2, KJV: Much every way: chiefly, because that unto them were committed the oracles of God.

Paul states that the "oracles of God" were given to the Jews, which necessitates an affirmation of the books affirmed by the Jews. Now, it is true that the Sadducees and the Pharisees differed in their canon, as the Sadducees only accepted the Mosaic, however it is clear that Paul (from a Pharisaic background) would refer to the Pharisaic canon. Additional evidence is that Paul always quotes books from the Jewish Pharisaic canon, not the Essene or Sadduceeic canon.

8: The book of Revelation contains prophecies, which proves its inspiration.

Depiction of the the Fourth Angel in Rev 8

Revelation 2:8-11 prophesied the persecution that came to Smyrna around 140ad, when Polycarp was also killed.

Revelation 13:17 prophesied digital currency.

Revelation 22:18-19 implies foreknowledge on the book of Revelation being the book with the most variants. We know from history that the book of Revelation was carelessly copied, and yet the same book with the most variants, has the harshest warning on editing the book. This is a prophecy by implication, that the book would be carelessly copied.

Revelation 9:17 maybe prophesied modern warfare, as it talks about "fire and smoke" being used as weapons, this likely refers to modern weaponry, such as guns.

 Revelation 9:16 prophesied modern population growth, as the verse describes an army of 200million, yet there were not yet even so many people in the world. 

Revelation 7:9 describes the spread of Christianity to the entire world and to every nation, which is today already fulfilled.

9: The epistle of John speaks authoritatively

1 John 2:22

Who is a liar but he that denieth that Jesus is the Christ? He is antichrist, that denieth the Father and the Son.

1 John 2:18

18 Little children, it is the last time: and as ye have heard that antichrist shall come, even now are there many antichrists; whereby we know that it is the last time.

Now anyone can make such claim, yet if an apostle makes the claim, we can have much confidence that he is speaking the truth, otherwise why would God have chosen him for the duty of spreading the gospel?

10: if Revelation is inspired, there is reason to think that the rest of the Johannine writings are

Now there is some debate on the authorship of Revelation, Eusebius argued that the book was written by a close companion of John the apostle, called John the elder, he argued that Papias (60 – 130) made the same distinction. Now, there is no objection to such an authorship, as Luke was inspired despite not being an apostle, though he was a close companion of Paul. Yet others, such as Justin Martyr (100 – 165) attributed Revelation to the apostle himself, and this has been the majority opinion of Christians in history. Nevertheless, in both cases, the authority of the Johannine corpus is established. 
If Revelation is inspired and written by John the apostle, why would not other of his writings that were preserved to this day too? If it was written by a close disciple of John, why wouldn't the preserved writings of his master be inspired too, especially if they speak authoritatively?

11: What about James, Jude and perhaps Hebrews?

Now if Hebrews was written by Paul, that goes simultaneously. However others believe that the author was Barnabas (this was the opinion of Tertullian), in these three cases, we have less direct evidences, yet their agreement with other scriptures, their content and apostolic authorship along with being preserved to our day, together make a case for their inclusion in the canon.

12: The Old Testament prophesied the future

We also can know the validity of the Old Testament due to the many prophesies in contains (such as Isaiah 53, Psalm 22, Ezekiel 26 etc.).