Scripture should be used as the basis for our beliefs.
Christ referred to the Penteteuch, the Prophets, and the Psalms. These are the scriptures before the apostles, et. al., wrote the New Testament.
He said to them, “This is what I told you while I was still with you: Everything must be fulfilled that is written about me in the Law of Moses, the Prophets and the Psalms.”
Jesus claimed to be God, and the Jews knew it.
16 So, because Jesus was doing these things on the Sabbath, the Jews persecuted him. 17 Jesus said to them, “My Father is always at his work to this very day, and I, too, am working.” 18 For this reason the Jews tried all the harder to kill him; not only was he breaking the Sabbath, but he was even calling God his own Father, making himself equal with God.
30 I and the Father are one.”
31 Again the Jews picked up stones to stone him, 32 but Jesus said to them, “I have shown you many great miracles from the Father. For which of these do you stone me?”
33 “We are not stoning you for any of these,” replied the Jews, “but for blasphemy, because you, a mere man, claim to be God.”
7 The Jews insisted, “We have a law, and according to that law he must die, because he claimed to be the Son of God.”
Jesus also said the Holy Spirit would teach the apostles all things, reminding them of everything Christ told them.
But the Counselor, the Holy Spirit, whom the Father will send in my name, will teach you all things and will remind you of everything I have said to you.
The apostle Peter said that Paul’s writings were scripture.
2 Peter 3:15-16
15 Bear in mind that our Lord’s patience means salvation, just as our dear brother Paul also wrote you with the wisdom that God gave him. 16 He writes the same way in all his letters, speaking in them of these matters. His letters contain some things that are hard to understand, which ignorant and unstable people distort, as they do the other Scriptures, to their own destruction.
Paul said all scripture is Go breathed and useful for teaching, rebuking, correcting, and training in righteousness.
2 Timothy 3:16
All Scripture is God-breathed and is useful for teaching, rebuking, correcting and training in righteousness
Paul also said to test everything and keep the good.
1 Thessalonians 5:20-22
20 do not treat prophecies with contempt. 21 Test everything. Hold on to the good. 22 Avoid every kind of evil.
The Bereans gave an example of how to test what people say is true or not, by examining the scriptures.
Now the Bereans were of more noble character than the Thessalonians, for they received the message with great eagerness and examined the Scriptures every day to see if what Paul said was true.
So we must turn to Scripture as the basis for doctrine, church matters, and how we should live our lives.