I bet you have never heard that statement before,have you?
You see the “Word” was and is an orally presented message, that just happens to be written down for us to see now. It is because of mankind’s need to see things written down to have them to read as an individual’s opportunity to have in one’s own possession that it has changed in the last 500 years. It was the advancement of the printing press that has given us the masses this chance to all see,read and interrupt the words of all things orally read aloud for the crowds. It was only before this time that the records of all orally decreed messages of men were only kept as an archive for print.
This concept thus becomes important to our understanding of the “word” of God. God’s desire for us to ‘hear’ the word was more important to him, than to read it on black and white paper. This is what Jesus was telling the Pharisee’s and Sadducees that tho they ‘read the word’ over and over again, they still did not hear the message. It was not in the written word but in the message within the words. There is a difference!
God’s Spirit is within the “oral word”, His spirit talks to us in a more distinct way than just the words of the bible.
The Eternal Purpose 
You referenced Jesus telling the Pharisees and Sadducees to understand the Word, He was showing them that He was the Lamb of God, the Messiah of the Old Testament. It is very simple, not complex. Men try to make it complex but what Jesus taught and warned mankind is that there is a hell- mankind must come to God through his sacrifice – the blood which pays for our sins. If we accept Him we have fellowship with God now and we are in His kingdom. It really is simple,but mankind has convoluted and complicated it to the point that any are damned and on there way to hell. They serve there gods or create and fashion a god that fits what they want. Just like the days of the Old Testament, we live in a world that is racing to Gods judgement and people that say they are Christians don’t heed the words of Christ, they must wake up and begin to warn the masses.