Now I am aware that this admonition in context is speaking of the prophecy. However a similar text shows up in Jeremiah 23. There, rather than sharing the Word of God the prophets were sharing their own ideas. If you read the chapter you will find God was not happy with them.
We wouldn't do that now, would we?
There are times when there is not a lot of data about what is happening in the narrative. We see people acting, interacting with Christ, but their motives and their thinking is not clearly revealed. In some cases their motivation is revealed. In the case where it is not, if we are called upon to teach or share on that passage there is a lot of pressure to supply that motivation or to explain the thinking of those involved. There are commentators who will suggest motivation or thinking should we not be creative ourselves.
A couple of years ago I was working through Bible study methods with a group in another country. I use 2 Peter in those situations. One of the things I ask people to do is to try to determine when the book was written from observation only. The answer is found in 2 Peter 1:14, Peter knows that he is at the end of his life.
One of the men asked how old Peter was when he died. I told him I did not know. He said he wanted to know; that it would help him better understand the text. Less bluntly than I am going to write it here I told him that it would not and that apparently it was not data that was important.
Why did I say that? There are many examples in the Bible where the Holy Spirit did tell us how old men were when they died. Apparently, we need to know that information. Not so with Peter. If we add it, are we not adding to the text?
The same may be true when we try to supply motivation or thinking that is not in the text. My point is that what the Spirit inspired men to write in the Bible, according to Paul, in 2 Timothy 3:14 – 17, is profitable – well you can read it. It seems that it should be adequate to observe what is being said well, rather than speculate what could have been said.