12 When, therefore, the Lecture is delivered, if a Catechumen ask you what the teachers have said, tell nothing to him that is without. For we deliver to you a mystery, and a hope of the life to come. Guard the mystery for Him who gives the reward. Let none ever say to you, What harm to you, if I also know it? So too the sick ask for wine; but if it be given at a wrong time it causes delirium, and two evils arise; the sick man dies, and the physician is blamed. Thus is it also with the Catechumen, if he hear anything from the believer: both the Catechumen becomes delirious (for he understands not what he has heard, and finds fault with the thing, and scoffs at what is said), and the believer is condemned as a traitor. But you are now standing on the border: take heed, pray, to tell nothing out; not that the things spoken are not worthy to be told, but because his ear is unworthy to receive. You were once yourself a Catechumen, and I described not what lay before you. When by experience you have learned how high are the matters of our teaching, then you will know that the Catechumens are not worthy to hear them.
Source: Catechetical Lectures (New Advent)