You will find in researchers who, with the capital of their intellect, write every corruption related to creed, whether with or without evidence, out of the fanaticism in which they are immersed. If one doubts this, that person is someone whose religion is corrupt. But if one believes in it, he is someone who feels secure from Allah's punishment and is deceived by his deficient intellect. No one who plunges into such investigation can escape these two states. However, if one transcends the limits of the rational and passes into the light of unveiling (mukāshafa) that shines in the realm of sainthood (walāya) and prophethood (nubuwwa), he is saved from this state. This is what is called kibrit-i ahmar (literally, 'red sulphur' or 'ruby' in the dictionary). I am optimistic about this matter. Only the common people (ʿawām) whose intellect is limited, or those who, out of fear of Hell, are occupied with obedience to Allah, can be saved from this danger. They do not indulge in such unnecessary matters. (Iḥyāʾ, IV, 216-217)
Regarding mewt-i mānevī (spiritual death), (Shaykh ʿAbd al-Qādir al-Jīlānī) said: If you die by separating from people, it is said, 'May Allah have mercy on you and restrain you from your caprice (hawā).' If you die by separating from your caprice, it is said, 'May Allah have mercy on you and separate you from your will (irāda).' If you separate from your will, it is said, 'May Allah have mercy on you and revive you with a life after which there is no death.'
May He grant you a gift that cannot be prevented, may He grant you a comfort after which there is no distress, may He bestow upon you a blessing after which there is no hardship, may He teach you a knowledge after which there is no ignorance, may He grant you a security after which there is no fear (khawf).
Thus, you attain felicity and are not afflicted with distress; you find honor and are not humiliated; you draw near and are not distanced; you are elevated and not abased; your worth increases and you gain value, you are not despised. You are purified and not stained.
kil-i aqwām (the primordial clay) is realized in you, words are verified in you. Thus, you become kibrit-i ahmar (red sulphur or a precious mineral like ruby), you become a rare and precious human being, not easily found.
You become a unique, peerless ferīd (singular one), a wāḥid (one without kind), the unseen of the unseen and the secret of the secret (of a human being). In this state, you become the inheritor of all the prophets and the ṣiddīqūn (the truthful ones).
Sainthood (walāya) is completed in you, substitutes (abdāl) are attributed to you; sorrows are removed through you, rains fall because of you, crops grow because of you, calamities are repelled through you, all specific and general hardships are removed through you. (Futūḥ, 10-11)