10You, however, know all about my teaching, my way of life, my purpose, faith, patience, love, endurance, 11persecutions, sufferings—what kinds of things happened to me in Antioch, Iconium and Lystra, the persecutions I endured. Yet the Lord rescued me from all of them. 12In fact, everyone who wants to live a godly life in Christ Jesus will be persecuted, 13while evil men and impostors will go from bad to worse, deceiving and being deceived. 14But as for you, continue in what you have learned and have become convinced of, because you know those from whom you learned it, 15and how from infancy you have known the holy Scriptures, which are able to make you wise for salvation through faith in Christ Jesus. 16All Scripture is God-breathed and is useful for teaching, rebuking, correcting and training in righteousness, 17so that the man of God may be thoroughly equipped for every good work.In verse 14 Paul talks about "what you have learned and from whom you have learned it." The preceding verses remind Timothy of some of the things Paul and Timothy went through. Notice Paul does not appeal to an objective impartial reading of scripture. Before he mentions scripture he mentions reasons to trust him as a man of God. Remember Jesus didn't say, "Here is the truth." He said, "I am the way, the truth and the life." Paul is following that. He is not focusing on a plan but a person, himself. He contrasts himself with those "having the form of godliness but denying it's power(vs 5)". Essentially Paul is saying Timothy should listen to him because he is a saint.
Then he talks about scripture. What does scripture means here? Probably the Septuagint. Timothy knew them as an infant. Paul does not hint at any books being added. So neither Paul nor Timothy have the New Testament in view here. Did the Holy Spirit have it in view? You can make that assumption but it is an assumption. It is not clear in the text. Catholics do apply what these verses say to the New Testament as well but that does not flow trivially from this verse. We base it on other statements the church has made about the bible that clearly apply to the New Testament.
Then we get down to the verses protestants actually quote, verses 16 and 17. What do they say? First of all, scripture is God-breathed or inspired by God. This is amazingly important. It is stronger than saying it is inerrant. It means God chose these words to make Himself known. It means we need to read them. We need to memorize them. We need to reflect on them. When Catholics deny Sola Scriptura they do not deny the importance of the bible. Quite the opposite. What Catholics say is it is so important it must be read in the right light so it does not get distorted. It is so good that if we twist it to our own desires we can do great evil.
So it says it is inspired and then it says it is useful. Useful for teaching, rebuking, correcting and training in righteousness. Does that imply that nothing else is useful for teaching, rebuking, correcting and training in righteousness? No. This was obviously written before Paul was killed around 66 AD. So there would still be people who had heard Jesus preach. Certainly there were many who had heard Paul preach. Would those words be useful for teaching, rebuking, correcting and training in righteousness? Of course. Paul is not denying the usefulness of everything else God has done. So the Sola part of Sola Scriptura just isn't here. There is no hint of it. To say it is is to twist the word of God.
Then we have the phrase "man of God". This could mean an ordained person. It certainly does not mean a novice Christian. It means somebody who has been formed in the faith to some degree. But then such a person needs to be taught, rebuked, corrected and trained in righteousness. By whom? By the scriptures? Hardly. Somebody has to use the scriptures to do that. That is how people get equipped for every good work. Timothy was to use the scriptures to form other men of God? Does that exclude the passing on of tradition? On the contrary, it is assumed that Timothy's way of interpreting scripture would be passed on.