And in the synagogue there was a man who had the spirit of an unclean demon, and he cried out with a loud voice, “Ha! What have you to do with us, Jesus of Nazareth? Have you come to destroy us? I know who you are—the Holy One of God.” — Luke 4:33-34 ESV
We should notice, in this passage, the clear religious knowledge possessed by the devil and his agents. Twice in these verses we have proof of this. “I know you who you are, the holy one of God,” was the language of an unclean devil in one case. “You are Christ the son of God,” was the language of many devils in another. Yet this knowledge was a knowledge unaccompanied by faith, or hope, or charity. Those who possessed it were miserable fallen beings, full of bitter hatred both against God and man.
Let us beware of an unsanctified knowledge of Christianity. It is a dangerous possession, but a fearfully common one in these latter days. We may know the Bible intellectually, and have no doubt about the truth of its contents. We may have our memories well stored with its leading texts, and be able to talk glibly about its leading doctrines. And all this time the Bible may have no influence over our hearts, and wills, and consciences. We may, in reality, be nothing better than the devils.
Let it never content us to know religion with our heads only. We may go on all our lives saying, “I know that, and I know that,” and sink at last into hell, with the words upon our lips. Let us see that our knowledge bears fruit in our lives. Does our knowledge of sin make us hate it? Does our knowledge of Christ make us trust and love Him? Does our knowledge of God’s will make us strive to do it? Does our knowledge of the fruits of the Spirit make us labor to show them in our daily behavior? Knowledge of this kind is really profitable. Any other religious knowledge will only add to our condemnation at the last day.