Satan

Shall we not free ourselves from the horror of satanic gloom, and hasten towards the rising light of the heavenly Beauty?

Bahá’u’lláh, Kitáb-i-Íqán, p. 38

There can be no doubt whatever that, in consequence of the efforts which every man may consciously exert and as a result of the exertion of his own spiritual faculties, this mirror can be so cleansed from the dross of earthly defilements and purged from satanic fancies as to be able to draw nigh unto the meads of eternal holiness and attain the courts of everlasting fellowship.

Bahá’u’lláh, Gleanings from the Writings of Bahá’u’lláh, p. 262

Give greetings to thy dear mother. Superstitions hath somewhat overcome her. When the imagined Satan overpowers let her say: 'O Bahá-el-Abhá!" She should then turn to the highest Kingdom. Thus will the imagined Satan leave her. (She) has a form of obsession; therefore, you may not heed her sayings.

‘Abdu’l-Bahá, Tablets of ‘Abdu’l--Bahá v1.p103

The reality underlying this question is that the evil spirit, Satan or whatever is interpreted as evil, refers to the lower nature in man. This baser nature is symbolized in various ways. In man there are two expressions, one is the expression of nature, the other the expression of the spiritual realm. The world of nature is defective. Look at it clearly, casting aside all superstition and imagination. If you should leave a man uneducated and barbarous in the wilds of Africa, would there be any doubt about his remaining ignorant? God has never created an evil spirit; all such ideas and nomenclature are symbols expressing the mere human or earthly nature of man. It is an essential condition of the soil of earth that thorns, weeds and fruitless trees may grow from it. Relatively speaking, this is evil; it is simply the lower state and baser product of nature.

‘Abdu’l-Bahá, Foundations of World Unity, p. 77