Q: What do the scriptures principally teach?
A: The scriptures principally teach what man is to believe concerning God, and what duty God requires of man.
John 5:39: You search the Scriptures because you think that in them you have eternal life; and it is they that bear witness about me,
How many times have we heard people, both Christian and non-Christian, say, "well my god is..." and then they continue on to give a description of a god of their own creation? A good example of this is an article I recently read by a "progressive" theologian. The article, which was written to describe how progressive Christians understand the Bible, of course, gave lip service to the Bible. But then the article went on to say that progressives do not believe that everything the Bible says is true and accurate. And what part of the Bible did the author reject? Any part that presents God as wrathful, vengeful, jealous, and so on. See, these attributes, in his mind, are simply incompatible with his god. The author wrote of a god full of love, compassion, patience, faithfulness, grace and mercy (I'm not sure what mercy means when there is no divine wrath, but that's a whole other topic!). Yes, the Bible certainly does reveal God to be all of those things, but the Bible also reveals God to be perfectly just, jealous, and full of wrath towards the unholy. The author of the article was not using the Bible to shape his understanding of God, rather, he was forming his own god based upon a fallen, human understanding of what he believes God should be. He openly discredited parts of God's word as simply being wrong if those portions of scripture presented attributes of God that seemed to contradict his mold.
This approach to understanding God, of course, has huge implications on his theology. Along with defining the rules and parameters of who he thinks God is, he goes on to form a set of rules and parameters of how a Christian should live and act based upon his view of God. Because this author was able to discredit a God of wrath, he is essentially able to justify any lifestyle, any sin, anything he wants based upon whether he deems it loving, fair, or in lines with his notion of justice.
We can all do this, can't we? We trust our fallen notions of fairness and justice, or love, or kindness, and then try to form a god who fits into our mold. It is idolatry, plain and simple, and here's the real kicker. Our own thoughts and opinions are not our guide to what we should believe concerning God. God himself has revealed his character and nature, and he has done it in the pages of scripture. Accept it as revelation, or reject it as revelation, but there is no middle ground here. The Bible alone gives us the revelation we need to know who God is, and if we seem to feel that there are contradictions in how God has revealed himself in the scriptures, then the problem is not in God's revelation, but rather, in our understanding of it. We are not free to simply cast aside portions of the Bible that we believe present God to be something we don't like. We must let the revelation of God mold and shape our understanding of God, not let our understanding of God mold and shape what we think the Bible says, or what God should or shouldn't be like. And once we are able to see who God truly is, as he has revealed himself to be in scripture, then we are able to see what duty God requires of us. In other words, you cannot have orthopraxy (right living) if you do not first have orthodoxy (right belief).
How does all of this relate then to Christ's words in John 5:39? It's actually quite remarkable what Jesus is saying here. He reveals to us in these words that he is God in the flesh, and that he is the fulfillment of all Biblical revelation. The Old Testament laws and rituals? They point to him! Do we want to know what God is like and what he requires of us? Then look in faith to Jesus Christ himself! Look as his character, his attributes, his life of perfect obedience, and his substitutionary death on the cross.