A few weeks ago I heard someone comment that "we need to go back and read the Bible verses that aren't underlined or highlighted." I like that!
Why do we need to read the verses that aren't underlined or highlighted?
That is a way of saying that we need to be thorough in our Bible study. We often become attached to certain statements we have "underlined or highlighted," favorite verses and pleasant topics that attract our attention. But we may be skipping over those verses that are less exciting, more difficult, more time consuming, or, God forbid, something we don't want to hear or think about.
Get all you can out of the verses that are underlined or highlighted -- but don't forgot about the wealth of the rest of the material that God has revealed in His Word. It is ALL God's Word. All Scripture is given by inspiration of God and is profitable. We need it all to get the whole picture, to understand the fullness of God's revelation to us.