To give prudence to the simple, knowledge and discretion to the youth--
Let the wise hear and increase in learning.
Proverbs 1:4,5
Schools have to use different textbooks for students who are at different levels in their education. First graders who are just learning to add and subtract can't use the same books used by high school and college students studying subjects such as algebra and calculus. But the Bible is different from books written by men. As the above quote shows, it can be used by people at any stage of their spiritual growth, whether they are classed among the simple or the wise. My own experience confirms that this is true. I have been a Christian for almost 52 years. When I became a Christian I began reading the Bible regularly and found it essential to my spiritual growth. (I had read the Bible even before I was a Christian, but I didn't understand it very well because I was lacking the relationship with God which is the center of its message.) But altho I have been studying the Bible for so long I find that I have never outgrown it as I have the textbooks I used when I was in grade school, but I am still learning more things from it.