All scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness:
2 Timothy 3:16 (KJV)
Doctrine – Now that we’ve established what Paul is referring to as scripture, we can dig into the rest of this verse. When Yeshua was challenged, or the Apostles confronted, what did they use to support their actions? The Tanakh. When Yeshua commenced his sermon on the mount, from where did He quote? The Tanakh. When Paul writes his letters, from where did he teach? The Tanakh. Scripture, which Paul defined as the Tanakh, was the basis of doctrine.
The Greek word didaskalia, being used here as “doctrine”, differs from its counterpart didache in that the latter refers to the substance of teaching while the former is the act of teaching. So didaskalia is the process by which a didaskalos (teacher) teaches. Searching further into the definition of this word, we find that didaskalia is the teaching that belongs to the teacher which carries a very Greek viewpoint. Paul and the other rabbis understood this a bit differently.
In general didaskalia is not a suitable word in Judaism and the NT, since the didaskalos has no didaskalia of his own.
Theological Dictionary of the New Testament, 166
This is because the Biblical teachers of the time understood that the process by which they taught was not their own, but rather it was from God. And in order to be from God, the teachings would have to be rooted in the Tanakh. Have you ever noticed that Yeshua never taught anything new? Everything He mentions comes directly from the Tanakh. Paul never taught against the law, he taught against the use of the law for salvific purposes, which likewise was taught in the Tanakh.
So what does this tell us? If we’re to use the Apostolic process of teaching as our example, then we cannot pull verses from the New Testament and base entire doctrines on them without exact references from the Tanakh that support it completely. Any doctrine created must be rooted in the Old Testament, in Scripture, according to Paul. Often times we like to take a verse from the New Testament solely as proof of a particular belief, but if it’s not supported by the Tanakh, then we’re either misinterpreting the NT verse, or it has to be false. Does that sit well with you? Any verse in the New Testament must measure up with Torah in order to be true. The Bereans were perceived as more noble for searching the “scriptures” and comparing them against Paul’s teachings (Acts 17:11). If we submit that a verse from the New Testament opposes Torah, then we’re essentially stating that those particular NT verses are false. Might this cause you to read the Bible differently?
Do you know of doctrine that pits the New Testament against the Old? Practically every religion has some. These are what Paul and Yeshua taught against, especially when they were placed above the doctrine of God – His commandments, statutes, and judgments. So as Paul directs Timothy, let us take from this teaching as well. All Scripture (the Old Testament) is to be used for the development of doctrine. From this beginning, and on this foundation, we can then interpret the New Testament and all other writings, prophecy, and teachings.