Why couldn't I understand the Bible before I was saved?

Les explains that true biblical believing is where understanding begins: when a person can say, “I believe this,” it becomes plain as day, and that plainness is an act of God responding to faith. He illustrates this with a man who came into his class as a reprobate and could not fathom much of the Scripture. Les told him that when he ever became a believer, he would understand. Later, at Les’s kitchen table, they led him to the Lord through the Roman road, and his life changed. All of a sudden he could comprehend the Scripture. He later told Les that he goes to sleep reading the Book because he cannot get enough of it, whereas before he could not get any of it. Les uses this to show that this is where we have to come to, then moves to verse 6 about the old man, old Adam, the body and the sin-bent mind, will, and emotion, being crucified—crucifixion kills and puts to death.