Timothy was left in Ephesus because there were some teachings things that ought not to have been taught (1:3). This means there is a right teaching and any teaching that is contrary to that correct teaching is a teaching not from God. This plays a significant role when we get to C-2, and in today’s 21st century.
What is that right or correct teaching? Rather than identify particular points, we can learn more when we notice the words of Peter, “if any man speaks, let him speak the oracles (words) of God” (1 Peter. 4:11a, ASV). From this we learn that one must say nothing more than that which the Lord said in Scripture. Paul lived by this way of thinking, “For I will not dare to speak of any things save those which Christ wrought through me, for the obedience of the Gentiles, by word and deed” (Romans 15:18). So serious was this to Paul, that he wrote to the churches in Galatia, “But though we, or an angel from heaven, should preach unto you any gospel other than that which we preached unto you, let him be anathema” (Galatians 1:8; cf. 1:6-9).
When Paul wrote to Timothy, there was a problem being addressed that was peculiar to his time, but the under-girding way to address that problem, as he did, was to begin with a standard that is not fluid, a standard that does not come from man, a standard that has its existence is the holiness of God.