From The Joy of Full Surrender
We can be truly instructed only by the words that God speaks to us personally. No one grows in knowledge of God either by reading books or by curious historical research. These means give us only a vain and empty knowledge, which serves only to confuse us and inflate us with pride.
That which truly instructs us is what comes to us by the will of God from moment to moment. This is the knowledge gained through experience, which Christ himself was pleased to acquire before teaching others. In fact, this was the only knowledge in which he could grow, according to the expression of the holy gospel, (Luke 2:52). This is because, being God, there was no degree of speculative knowledge that he did not already possess. Therefore if this experimental knowledge was useful to the Incarnate Word himself, it is absolutely necessary for us if we would touch the hearts of those whom God sends to us.
We know perfectly only what we have learned by experience through suffering or action. This is the school of the Holy Spirit, who speaks the words of life to the heart, and all that we say to others should come from this source. Whatever we read, whatever we see, becomes divine knowledge only by the fruitfulness, the virtue, the light that this experience gives. Without this experiential knowledge, all our learning is like dough made without yeast, lacking the salt and seasoning of experience. Without this experiential knowledge, we have only vague, untried ideas to act on. We are like the dreamer who, though he knows all the highways of the world, misses the road to his own house.
Therefore we have only to listen to God from moment to moment in order to become learned in the knowledge by which the saints lived, which is all practice and experience.
Set aside what is said to others, but listen to what is said to you and for you. You will find enough in that to exercise your faith, because this interior language of God, by its very obscurity, exercises, purifies, and increases your faith.