A.W. Tozer emphasizes that spiritual truths can only be understood by those who are pure in heart, as they require divine illumination rather than mere intellectual comprehension. He references 1 Corinthians 2:14, highlighting that the natural man cannot grasp the things of the Spirit, which are often seen as foolishness to him. Tozer points out that this concept is crucial for understanding the teachings of Jesus as presented in the Gospel of John and throughout the New Testament. He also notes that the necessity for spiritual discernment is echoed in the wisdom literature of the Old Testament, reinforcing the idea that true understanding comes from a heart aligned with God. Ultimately, Tozer calls for believers to seek spiritual enlightenment to fully appreciate the depth of divine truths.

Surely God has that to say to the pure in heart which He cannot say to the man of sinful life. But what He has to say is not theological, it is spiritual; and right there lies the weight of my argument. Spiritual truths cannot be received in the ordinary way of nature. "The natural man receiveth not the things of the Spirit of God: for they are foolishness unto him: neither can he know them, because they are spiritually discerned" (1 Cor. 2:14). So wrote the apostle Paul to the believers at Corinth. Our Lord referred to this kind of Spirit-enlightened knowledge many times. To Him it was the fruit of a divine illumination, not contrary to but altogether beyond mere intellectual light. The fourth Gospel is full of this idea; indeed the idea is so important to the understanding of John's Gospel that anyone who denies it might as well give up trying to grasp our Lord's teachings as given by the apostle John. And the same idea is found in John's first epistle, making that epistle extremely difficult to understand but also making it one of the most beautiful and rewarding of all the epistles of the New Testament when its teachings are spiritually discerned. The necessity for spiritual illumination before we can grasp spiritual truths is taught throughout the entire New Testament and is altogether in accord with the teachings of the Psalms, the Proverbs and the Prophets. The Old Testament Apocrypha agrees with the Scriptures here, and while the Apocryphal books are not to be received as divinely inspired, they are useful as showing how the best minds of ancient Israel thought about this matter of divine truth and how it is received into the human heart.