People of wisdom state:
If the names of the Awliya' [dear slaves of Allah] are mentioned with love, their souls will be present at that place, and mercy will shower there. As a matter of fact, a hadith-i sharif says, "Mercy descends where the pious are mentioned." Whoever reads a book by such a great personality, he will experience a constant, spiritual contact with him. Just as a lamp produces light when a switch is pushed, so, in order to get benefit from the spirituality of these Islamic superiors, it is necessary to mention their names with due respect or to make mention of something that will remind us of them. This contact and love is a source of spiritual outpourings [that flow from their hearts].
The spirituality of a writer is with his books. Therefore, if the author of a book is good, his pure soul [while his book is being read] comes and radiates spiritual outpourings, which cause the [reader's] heart to become purified. If its author is bad, his wicked soul radiates evil, which causes the [reader's] heart to darken.
One day, while a great person was delivering a religious speech, one of his disciples came in. That holy person asked:
"A disgusting, nasty smell is emanating from you. What is it?"
"Sir, getting up in the morning, I performed a ritual bath and put on new underwear. All my clothes are clean," the disciple answered.
This incident staggered other disciples at attendance because he was not an outsider, but their friend whom they knew well.
"Okay, pull out whatever is in your pockets," he ordered.
The disciple took a book first out of his pocket. When his master saw the book, he inquired:
"There is no need for you to pull anything from your pocket. Where did you get this book?"
"Sir, while I was coming here, a friend of mine, as he knew my piety, said, 'I will give you a good Islamic book.' As it was a religious book, I accepted it happily and put it in my pocket," he said.
After reading a few pages of it, his master told:
"All the Islamic knowledge in this book may be correct, but the darkness issuing from the wicked soul of its author covers everyone. Take it out of here immediately!"
The poisonous book
Once, some people brought a great person a small book entitled Dinim [My Religion] written by someone named Sharaf ad-Din Effendi. After he had it read aloud from cover to cover and listened to it, he said:
"From beginning to end, not even one word of it is wrong. But whoever reads it will get poisoned because its author is an evil man."
If the author of a book meets all the necessary qualifications and all of what he has written is correct but if his book has been published for gain and fame or if there are other thoughts contrary to our religion, that book, too, radiates evil. For this reason, in the translations of the books by such notable figures as Imam al-Ghazali and Abd al-Qadir Gaylani, it is possible to see the darkness mentioned above because of the intentions their translators and publishers have.