From the Philokalia, which I find has to be read very slowly.
He who seeks to understand commandments without fulfilling commandments, and to acquire such understanding through learning and reading, is like a man who takes a shadow for truth. For the understanding of truth is given to those who have become participants in truth (who have tasted it through living). Those who are not participants in truth and are not initiated therein, when they seek this understanding, draw it from a distorted wisdom. Of such men the Apostle says: ‘the natural man receiveth not the things of the Spirit’ (I Cor. ii. 14) even though they boast of their knowledge of truth.
Gregory of Sinai