Hmmm. I see your point. You think that a faith "delivered once" to the saints couldn't possibly develop in undertanding.
Yes, the Christian Faith was given in its entirety by the time Jude wrote. The Good News had come: the Messiah had arrived and accomplished the work which would translate those who received Him from the kingdom of darkness into HIS kingdom. The disciples of Jesus Christ had learned all that was needed from the Head of the Body, the Church, and they were spreading His word, making disciples, baptizing, and teaching them to observe all that the Head commanded them.
It isn't that this faith "delivered once" to the saints couldn't possibly develop in understanding. No, our understanding, our comprehension grows ever brighter as we walk with God. "The path of the righteous is like the light of dawn that shines brighter and brighter until the full day" (Prov. 4:18) The body of truth given by God does not grow or change over time; it needs no embellishment; it is perfect AS IS. What develops is our understanding of it (and obedience to it).
Then it seems that we agree that our understanding can grow. Now let's discuss this "needs no embellishment."
If the body of truth does not change, but our understanding does, are we forbidden to try to capture this better understanding? To write it down, classify, clarify, define it? If something is true by revelation or true by deduction isn't it still true? If we name a concept of this understanding, even if the name isn't in Scripture, isn't it still true?
If it needs no embelishment, why do we type these words? Why do we make textbooks for our children? Why do we print study guides and concordances?
SD