. . . for the soul is prone to evil.

Bahá’u’lláh, The Summons of the Lord of Hosts, p. 199

Indeed the actions of man himself breed a profusion of satanic power. For were men to abide by and observe the divine teachings, every trace of evil would be banished from the face of the earth. However, the widespread differences that exist among mankind and the prevalence of sedition, contention, conflict and the like are the primary factors which provoke the appearance of the satanic spirit. Yet the Holy Spirit hath ever shunned such matters. A world in which naught can be perceived save strife, quarrels and corruption is bound to became the seat of the throne, the very metropolis, of Satan.

Bahá’u’lláh, Tablets of Bahá’u’lláh Revealed after the Kitab-i-Aqdas, p. 176-177

The source of all evil is for man to turn away from his Lord and set his heart on things ungodly.

Bahá’u’lláh, Tablets of Bahá’u’lláh, p. 156

Evil is non-existent; it is the absence of good; sickness is the loss of health; poverty the lack of riches. When wealth disappears you are poor; you look within the treasure box but find nothing there. Without knowledge there is ignorance; therefore ignorance is simply the lack of knowledge. Death is the absence of life. Therefore on the one hand we have existence; on the other, nonexistence, negation or absence of existence.

‘Abdu’l-Bahá, Foundations of World Unity, p. 76-79

In creation there is no evil; all is good. Certain qualities and natures innate in some men and apparently blameworthy are not so in reality. For example, from the beginning of his life you can see in a nursing child the signs of desire, of anger, and of temper. Then, it may be said, good and evil are innate in the reality of man, and this is contrary to the pure goodness of nature and creation. The answer to this is that desire, which is to ask for something more, is a praiseworthy quality provided that it is used suitably. So, if a man has the desire to acquire science and knowledge, or to become compassionate, generous and just, it is most praiseworthy. If he exercises his anger and wrath against the bloodthirsty tyrants who are like ferocious beasts, it is very praiseworthy; but if he does not use these qualities in a right way, they are blameworthy. ... It is the same with all the natural qualities of man, which constitute the capital of life; if they be used and displayed in an unlawful way, they become blameworthy. Therefore it is clear that creation is purely good.

‘Abdu’l-Bahá, Some Answered Questions, pp. 250- 251

Nevertheless a doubt occurs to the mind -- that is, scorpions and serpents are poisonous. Are they good or evil, for they are existing beings? Yes, a scorpion is evil in relation to man; a serpent is evil in relation to man; but in relation to themselves they are not evil, for their poison is their weapon, and by their sting they defend themselves. But as the elements of their poison do not agree with our elements -- that is to say, as there is antagonism between these different elements, therefore, this antagonism is evil; but in reality as regards themselves they are good. The epitome of this discourse is that it is possible that one thing in relation to another may be evil, and at the same time within the limits of its proper being it may not be evil. Then it is proved that there is no evil in existence; all that God created He created good. This evil is nothingness; so death is the absence of life. When man no longer receives life, he dies. Darkness is the absence of light: when there is no light, there is darkness. Light is an existing thing, but darkness is nonexistent. Wealth is an existing thing, but poverty is nonexisting. Then it is evident that all evils return to nonexistence. Good exists; evil is nonexistent.

‘Abdu’l-Bahá, Some Answered Questions, p. 263-264