This is an Aplogetics 101 question: and any person with a BASIC understanding aplogetics should be able to answer this.
hint: the anwser is NOT “because the Church said so.”
You can goolge as well as anyone else for the answer if you didn’t know:
equip.org/perspectives/bible-authority
gotquestions.org/Bible-inspired.html
carm.org/christianity/bible/bible-isnt-word-god-it-contains-word-god
etc etc
Bible Reliability-Prophecy
The third principle of Bible reliability is Prophecy, or predictive ability. The Bible records predictions of events that could not be known or predicted by chance or common sense. Surprisingly, the predictive nature of many Bible passages was once a popular argument (by liberals) against the reliability of the Bible. Critics argued that the prophecies actually were written after the events and that editors had merely dressed up the Bible text to look like they contained predictions made before the events. Nothing could be further from the truth, however. The many predictions of Christ’s birth, life and death (see below) were indisputably rendered more than a century before they occurred as proven by the Dead Sea Scrolls of Isaiah and other prophetic books as well as by the Septuagint translation, all dating from earlier than 100 B.C.
Old Testament prophecies concerning the Phoenician city of Tyre were fulfilled in ancient times, including prophecies that the city would be opposed by many nations (Ezek. 26:3); its walls would be destroyed and towers broken down (26:4); and its stones, timbers, and debris would be thrown into the water (26:12). Similar prophecies were fulfilled concerning Sidon (Ezek. 28:23; Isa. 23; Jer. 27:3-6; 47:4) and Babylon (Jer. 50:13, 39; 51:26, 42-43, 58; Isa. 13:20-21).
Since Christ is the culminating theme of the Old Testament and the Living Word of the New Testament, it should not surprise us that prophecies regarding Him outnumber any others. Many of these prophecies would have been impossible for Jesus to deliberately conspire to fulfill — such as His descent from Abraham, Isaac, and Jacob (Gen. 12:3; 17:19; Num. 24:21-24); His birth in Bethlehem (Mic. 5:2); His crucifixion with criminals (Isa. 53:12); the piercing of His hands and feet at the crucifixion (Ps. 22:16); the soldiers’ gambling for His clothes (Ps. 22:18); the piercing of His side and the fact that His bones were not broken at His death (Zech. 12:10; Ps. 34:20); and His burial among the rich (Isa. 53:9). Jesus also predicted His own death and resurrection (John 2:19-22). Predictive Prophecy is a principle of Bible reliability that often reaches even the hard-boiled skeptic!
equip.org/articles/bible-reliability
There are also prophecies in the following books and letters. Why weren’t they considered the inspired, inerrant Word of God?
1.1 The Epistles of Jesus to Abgarus
2. Pseudo-apostolic (general) apocrypha
2.1 Teachings of the Twelve Apostles (Didache)
2.2 Epistle of the Apostles
- Pseudo-apostolic (specific - by Apostle) apocrypha
3.1 - Andrew -
3.1.1 Acts of Andrew
3.1.2 Acts of Andrew and Matthias*
3.2 - Barnabas -
3.2.1 Acts of Barnabas*
3.2.2 Epistle of Barnabas
3.2.3 Gospel of Barnabas
3.3 - Bartholomew -
3.3.1 Gospel of Bartholomew
3.3.2 Martyrdom of Bartholomew*
3.4 - James -
3.4.1 Apocryphon of James
3.4.2 Book of James (protevangelium)
3.4.3 First Apocalypse of James
3.4.4 Second Apocalypse of James
3.5 - John -
3.5.1 Acts of John
3.5.2 Acts of John the Theologian*
3.5.3 Apocryphon of John (long version)
3.5.4 Book of John the Evangelist
3.5.5 Revelation of John the Theologian*
3.6 - Mark -
3.6.1 Secret Gospel of Mark
3.7 - Matthew -
3.7.1 Acts and Martyrdom of St. Matthew the Apostle*
3.7.2 The Martyrdom of Matthew
3.8 - Nicodemus -
3.8.1 Gospel (Acts) of Nicodemus (aka The Acts of Pontius Pilate)
3.9 - Peter -
3.9.1 Acts of Peter
3.9.2 Acts of Peter and Andrew
3.9.3 Apocalypse of Peter - version 1
3.9.4 Apocalypse of Peter - version 2
3.9.5 Gospel of Peter
3.9.6 Letter of Peter to Philip
3.10 - Philip -
3.10.1 Acts of Philip
3.10.2 Gospel of Philip
3.11 - Thaddeus -
3.11.1 Acts of Thaddeus (Epistles of Pontius Pilate)*
3.11.2 Teaching of Thaddeus
3.12 - Thomas -
3.12.1 Acts of Thomas
3.12.2 Apocalypse of Thomas
3.12.3 Book of Thomas the Contender
3.12.4 Consumation of Thomas
3.12.5 Gospel of Thomas