Greetings!
One thing about the word of God is that it cannot be understood by human understanding or wisdom and this is because the word of God is spiritually motivated and inspired.
Furthermore, it's God that giveth understanding to his word and it's only through his spirit that we can understand his word.
Psalms 94:11 The LORD knoweth the thoughts of man, that they are vanity. In this scripture, we were made to know that the thoughts of man are vanity and a vain thought can never understand the word of God which is spirit filled.
Also in Proverbs 1:23 Turn you at my reproof: behold, I will pour out my spirit unto you, I will make known my words unto you.
In the above scripture as well, we were made to know that it's only through the outpouring of his spirit, God's spirit, that we can understand his word, which is the word of the bible.
1 Corinthians 1:19 For it is written, I will destroy the wisdom of the wise, and will bring to nothing the understanding of the prudent.
God in the above scripture also said that he would destroy the wisdom of the wise and the understanding of the prudent would bring to nothing, meaning, no wisdom or understanding of any man can be used to understand nor interpret the bible.
In conclusion, the central idea of this teaching is that no one can understand the word of God with their own wisdom or understanding, but by the spirit of God has been taught by Bro. Eli.
Thanks for reading.