Because that is where the Word of God was written as by the prophets of the OT. and 4 gospel writers.
No Pentateuch, Wisdom books, historical books in the OT? And no letters/epistles for the NT?
And how do you know that the Word of God is written in those books?
What is Doctrine? Can you clarify for me please?
Sure,
Definition of
DOCTRINE
1
archaic : teaching, instruction
2
a : something that is taught
b : a principle or position or the body of principles in a branch of knowledge or system of belief : dogma
c : a principle of law established through past decisions
d : a statement of fundamental government policy especially in international relations
e : a military principle or set of strategies
In the Bible you can find it referenced on these verses:
1 Corinthians 11:2
Now I praise you, brethren, that you remember me in all things and keep the traditions just as I delivered them to you.
2 Thessalonians 2:15
Therefore, brethren, stand fast and hold the traditions which you were taught, whether by word or our epistle.
2 Thessalonians 3:6
But we command you, brethren, in the name of our Lord Jesus Christ, that you withdraw from every brother who walks disorderly and not according to the tradition which he received from us.
Matthew 28:20
teaching them to observe all things that I have commanded you; and lo, I am with you always, even to the end of the age.” Amen.
Acts 28:30–31
30 Then Paul dwelt two whole years in his own rented house, and received all who came to him, 31 preaching the kingdom of God and teaching the things which concern the Lord Jesus Christ with all confidence, no one forbidding him.
1 Timothy 1:3
As I urged you when I went into Macedonia—remain in Ephesus that you may charge some that they teach no other doctrine,
1 Timothy 4:6
If you instruct the brethren in these things, you will be a good minister of Jesus Christ, nourished in the words of faith and of the good doctrine which you have carefully followed.
Acts 2:42
And they continued steadfastly in the apostles’ doctrine and fellowship, in the breaking of bread, and in prayers.
Romans 6:17
But God be thanked that though you were slaves of sin, yet you obeyed from the heart that form of doctrine to which you were delivered.
Romans 16:17
Now I urge you, brethren, note those who cause divisions and offenses, contrary to the doctrine which you learned, and avoid them.
1 Timothy 4:13
Till I come, give attention to reading, to exhortation, to doctrine.
1 Timothy 4:16
Take heed to yourself and to the doctrine. Continue in them, for in doing this you will save both yourself and those who hear you.
1 Timothy 5:17
Let the elders who rule well be counted worthy of double honor, especially those who labor in the word and doctrine.
2 Timothy 3:10–17
10 But you have carefully followed my doctrine, manner of life, purpose, faith, longsuffering, love, perseverance, 11 persecutions, afflictions, which happened to me at Antioch, at Iconium, at Lystra—what persecutions I endured. And out of them all the Lord delivered me. 12 Yes, and all who desire to live godly in Christ Jesus will suffer persecution. 13 But evil men and impostors will grow worse and worse, deceiving and being deceived. 14 But you must continue in the things which you have learned and been assured of, knowing from whom you have learned them, 15 and that from childhood you have known the Holy Scriptures, which are able to make you wise for salvation through faith which is in Christ Jesus. 16 All Scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness, 17 that the man of God may be complete, thoroughly equipped for every good work.
2 Timothy 4:1–5
1 I charge you therefore before God and the Lord Jesus Christ, who will judge the living and the dead at His appearing and His kingdom: 2 Preach the word! Be ready in season and out of season. Convince, rebuke, exhort, with all longsuffering and teaching. 3 For the time will come when they will not endure sound doctrine, but according to their own desires, because they have itching ears, they will heap up for themselves teachers; 4 and they will turn their ears away from the truth, and be turned aside to fables. 5 But you be watchful in all things, endure afflictions, do the work of an evangelist, fulfill your ministry.
Titus 1:7–9
7 For a bishop must be blameless, as a steward of God, not self-willed, not quick-tempered, not given to wine, not violent, not greedy for money, 8 but hospitable, a lover of what is good, sober-minded, just, holy, self-controlled, 9 holding fast the faithful word as he has been taught, that he may be able, by sound doctrine, both to exhort and convict those who contradict.
Titus 2:1
But as for you, speak the things which are proper for sound doctrine:
Titus 2:9–10
9 Exhort bondservants to be obedient to their own masters, to be well pleasing in all things, not answering back, 10 not pilfering, but showing all good fidelity, that they may adorn the doctrine of God our Savior in all things.
2 John 9–10
9 Whoever transgresses and does not abide in the doctrine of Christ does not have God. He who abides in the doctrine of Christ has both the Father and the Son. 10 If anyone comes to you and does not bring this doctrine, do not receive him into your house nor greet him;
The doctrine expressed here was entrusted to the Catholic Church. Just like Scriptures were entrusted to Her.
Your turn.