Scripture is there to reveal to us the heart, mind, and will of God. Therefore it is the Word of God. And it is totally sufficient for all believers and for all reasons (2 Tim 3:15-17). So to answer your question, we should not be looking at extra-biblical sources for enlightenment.
That's a misinterpretation of the passage you reference.
Are you going to use the Bible to plant in your garden if you want to harvest potatoes? How about to wash your car? Totally sufficient for all reasons?
The passage says that all scriptures is given that the man of God might be fully equipped.
It does not say that scripture is all that is given that the man of God might be fully equipped. I think you are interpreting it that way. The individual here is a 'man of God' before he can be fully equipped. The passage also talks about two sources of truth, the word he had heard, and the scriptures. Timothy grew up hearing the Old Testament. Then he heard the preaching of the Gospel.
You can give a soldier a rifle so that he might be fully equipped. That is a true statement. It means he is not fully equipped without the rifle. But it does not mean that the rifle is all he needs to be fully equipped. What if he had no helmet, uniform, or bullets. If you give him the rifle will be be fully equipped? Saying scripture is given than the man of God might be fully equipped implies he is not fully equipped without it, but it does not mean that it is all he needs.
As the soldier needs bullets, we need the stuff in the Bible, the stuff the Bible talks about. If you give someone a Bible and he has no faith and has no grace from God in his life, then he is not fully equipped to ever good work. The scriptures teach us about these things.
It does not make sense to say that we do not need baptism because we have the Bible, or that we do not need faith because we have the Bible. Nor does it make sense to say that we do not need spiritual gifts. I Corinthians even uses the word 'need' to describe individuals who have these gifts. One part of the body does not say to the other, "I have no need of thee." So we need the one gifted to prophesy, or the one with the gift of discernment of spirits, etc.
We still need the gift of teaching. Having a copy of the Bible is not sufficient.
We still need love. Having a copy of the Bible is not sufficient.
We still need faith. Having a copy of the Bible is not sufficient. Not without faith.
Scripture is given that the man of God might be fully equipped. The passage does not say that scripture is all that is given that the man of God might be fully equipped. It also does not mean that because we have the Bible we no longer need the things the Bible teaches us to have or teaches us that we need. It does not mean that because we have the Bible we no longer need to believe what it teaches... on spiritual gifts or other topics.
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