BEYOND GOOD AND EVIL : Article 295.
Genius of the heart: as it is possessed by that great Hidden One, the Tempter-God and born Rat- Catcher of the Conscience, whose voice can climb into the underworld of any psyche, who never speaks a word or looks a look in which there is not some hind-sight, some complexity of allure, whose craftsmanship includes knowing how to be an illusion -- not an illusion of what he is, but of what constitutes one more compulsion upon his followers to follow him ever more intimately and thoroughly -- genius of the heart which renders dumb all that is loud and complaisant, teaching it how to listen, which smooths rough souls and creates a taste in them for a new desire: to lie still like a mirror so that the deep sky might be reflected in them -- genius of the heart which teaches the bungling and precipitous hand to hesitate and handle things delicately, which guesses the hidden and forgotten treasure, the drop of goodness and sweet intelligence beneath layers of murky, thick ice; which is a divining rod for every speck of gold that lies buried in its dungeon of deep muck and sand -- genius of the heart, upon whose touch everyone departs richer, not full of grace, not surprised, not enriched and oppressed as though by strange goods, but richer in himself, newer than before, cracked wide open, blown upon and drawn out by a spring wind , more uncertain now perhaps, more delicate, fragile, and broken, but full of hopes that have no names as yet, full of new will and flow, full of new ill will and counterflow -- but what am I doing, my friends? Of whom am I speaking? Did I forget myself so far as not to tell you his name? Unless you yourselves have guessed who this questionable spirit and God is; who it is that demands such praise! For, as happens to everyone who from his early years has been a wanderer and an exile, many a strange and precarious spirit has run across my path. Foremost of all of them, and again and again, the one I was telling you about, no less a one that the God Dionysos, that great Ambivalent One and Tempter-God, the one to whom I once, as you know, in all secrecy and and reverence, sacrificed my first-born (having been the last, it seems to me, to sacrifice anything to him, for I found no one who understood what I was doing at that time). Meanwhile I learned much, all too much, about this God's philosophy by word of mouth, as I have said -- I, the last disciple and initiate of the God Dionysos.
(his "first-born" refers to his first book, The Birth of Tragedy
page 236-237 in the translation by Marianne Cohen