"[I]f a Catechumen ask thee what the teachers have said, tell nothing to him that is without. For we deliver to thee a mystery, and a hope of the life to come. Guard the mystery for Him who gives the reward. Let none ever say to thee, What harm to thee, 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 thou art 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. Thou wast once thyself a Catechumen, and I described not what lay before thee. When by experience thou hast learned how high are the matters of our teaching, then thou wilt know that the Catechumens are not worthy to hear them. "
– St. Cyril of Jerusalem, Catechetical Lectures, Prologue 12)
"Do not give dogs what is holy; and do not throw your pearls before swine, lest they trample them under foot and turn to attack you." – Matthew 7:6