Since, therefore, the Christians are not their own betrayers, it follows that it must be strangers. Now I ask, how could strangers obtain knowledge of us, when even true and lawful mysteries exclude every stranger from witnessing them, unless illicit ones are less exclusive? Well, then, it is more in keeping with the character of strangers both to be ignorant (of the true state of a case), and to invent (a false account). Our domestic servants (perhaps) listened, and peeped through crevices and holes, and stealthily got information of our ways.
…For no doubt, when any desire initiation in the mysteries, their custom is first to go to the master or father of the sacred rites.
Tertullian
Ad Nationes, Book I
Chapter III