Bahá’u’lláh, in the Kitáb-i-Aqdas, has exhorted us not to indulge our passions and in one of His well-known Tablets ‘Abdu’l-Bahá encourage us to keep our “secret thoughts pure”.
(Universal House of Justice, Lights of Guidance, p. 364)
But man hath perversely continued to serve his lustful appetites … With this, and with the perpetrating of vile and ignoble acts, his attention was engrossed, and he abandoned the temperance and moderation of a natural way of life. The result was the engendering of diseases both violent and diverse.
(‘Abdu’l-Bahá, Selections from the Writings of ‘Abdu’l-Bahá, pp. 152-153)
The heart must be sanctified from every form of selfishness and lust, for the weapons of the unitarians and the saints were and are the fear of God.
(‘Abdu’l-Bahá, A Traveller’s Narrative, p. 45)
The individual must be educated to such a high degree that he would rather have his throat cut than tell a lie, and would think it easier to be slashed with a sword or pierced with a spear than to utter calumny or be carried away by wrath. Thus will be kindled the sense of human dignity and pride, to burn away the reapings of lustful appetites. Then will each one of God’s beloved shine out as a bright moon with qualities of the spirit, and the relationship of each to the Sacred Threshold of his Lord will be not illusory but sound and real, will be as the very foundation of the building, not some embellishment on its facade.
(‘Abdu’l-Bahá, Selections from the Writings of ‘Abdu’l-Bahá, p. 136-137)
This physical world of man is subject to the power of the lusts, and sin is the consequence of this power of the lusts, for it is not subject to the laws of justice and holiness. The body of man is a captive of nature; it will act in accordance with whatever nature orders. It is, therefore, certain that sins such as anger, jealousy, dispute, covetousness, avarice, ignorance, prejudice, hatred, pride and tyranny exist in the physical world. All these brutal qualities exist in the nature of man. A man who has not had a spiritual education is a brute.
(‘Abdu’l-Bahá, Some Answered Questions, p. 119)