Is it true that 2 Timothy 3:16, when using the word "scripture", is really referring to the Old Testament writings and not the New Testament as being inspired?
Hebrew scripture was the only official scripture during early Christianity.
If you think about this one for a minute, you’ll know it has to be true. Anything we read in the New Testament was not official Scripture when it was written. When Paul wrote his letters, they were just that—letters written to specific individuals or churches who needed his counsel or to make a request. Same for all the letters. The Gospels and Acts were recorded in the hopes of preserving accounts of events that would serve as a way to evangelize those who had not heard of Jesus, and John shared his vision in the book of Revelation to encourage persecuted Christians in his day.
But all those individual pieces were not recognized as Scripture until hundreds of years later as church councils came together to sort out the many, many other accounts written about Jesus and the life of the church in those early years and try to decide which of them would serve as the authority for the faith and practice of the church. And even that happened in fits and starts with some books getting in many years before others. As late as the 17th century there were leaders like the reformer Martin Luther who wanted to axe both the book of James and Revelation from the New Testament.
If you want to know more about how the Bible was put together and how we ended up with the books that we did, you can read about it in this little study: What Is the Bible?that we published here at the Bible Society. (Note that another book with the same title exists by Rob Bell, that one is not ours.)
So when 2 Timothy 3:16 was written, the only official Scriptures in existence were the Hebrew Scriptures—what we have come to call the Old Testament (although it differs slightly from the actual Hebrew Scriptures with the books arranged differently and some different content here and there). The books that now comprise the New Testament couldn’t have been included because they were still being written. There was no such thing as the New Testament when 2 Timothy was written.
None of the New Testament authors would have presumed to put their writings on par with the Hebrew Scriptures, any more than a Christian author today would lay claim to calling their own work part of the Bible, even if they and others felt it was inspired by God. The status of Holy Scripture was conferred by elders and councils over time as they considered the reliability of the authors and had seen the fruit of their work as it was heard in faith communities and put to the test in the fires of daily life.
Does that mean the New Testament is not inspired by God and useful for teaching, correction, etc.? Not at all. It just means that 2 Timothy 3:16 is telling us that the Old Testament should not be cast aside as irrelevant. Now that 2 Timothy has been recognized by the church as part of the Bible, that verse reminds us that the Holy Bible is more than just the New Testament and that Christians should not ignore the stories, history, and prophetic voice that God inspired in and through Jewish life and faith for the millennia before Jesus walked the earth.
To close I will also note that Jesus also points us back to the Old Testament. When Jesus is asked in Matthew 22:37-38 what the greatest commandment is, Jesus answers by putting two Old Testament commandments together. The first, to love God with all your heart, soul, and strength comes from Deuteronomy 6:5 and love your neighbor as yourself is Leviticus 19:18. So it’s clear Jesus doesn’t want us to forget it either and points us directly to the most important parts.