Therefore I beg such lazy paunches or presumptuous saints to be persuaded and believe for God's sake that they are verily, verily! not so learned or such great doctors as they imagine; and never to presume that they have finished learning this [the parts of the Catechism], or know it well enough in all points, even though they think that they know it ever so well. For though they should know and understand it perfectly (which, however, is impossible in this life), yet there are manifold benefits and fruits still to be obtained, if it be daily read and practised in thought and speech; namely, that the Holy Ghost is present in such reading and repetition and meditation, and bestows ever new and more light and devoutness, so that it is daily relished and appreciated better, as Christ promises, Matt. 18:20: Where two or three are gathered together in My name, there am I in the midst of them.
Besides, it is an exceedingly effectual help against the devil, the world, and the flesh and all evil thoughts to be occupied with the Word of God, and to speak of it, and meditate upon it, so that the First Psalm declares those blessed who meditate upon the Law of God day and night. Undoubtedly, you will not start a stronger incense or other fumigation against the devil than by being engaged upon God's commandments and words, and speaking, singing, or thinking of them. For this is indeed the true holy water and holy sign from which he flees, and by which he may be driven away.
Now, for this reason alone you ought gladly to read, speak, think and treat of these things, if you had no other profit and fruit from them than that by doing so you can drive away the devil and evil thoughts. For he cannot hear or endure God's Word; and God's Word is not like some other silly prattle, as that about Dietrich of Berne, etc., but as St. Paul says, Rom. 1:16, the power of God. Yea, indeed, the power of God which gives the devil burning pain, and strengthens, comforts, and helps us beyond measure.