If anyone cares to ask why the violators of the Covenant should be avoided by loyal believers, this one sad episode would be answer enough. Khan came to see from this and other episodes that the violators are the serpent, the believers the hypnotized dove. Or to use another metaphor, the violators are sick with a mortal disease, and if the believers, by associating with them, hope to bring them back to health, all that happens is the believers are infected themselves. He noted that once the Covenant-breakers had won over a soul, they would cast that soul out. After all, what had they to give? Loyalty and love? They would not be faithful to anyone else, he reasoned, those who were not faithful to Bahá’u’lláh. And they were not outside enemies of the Faith, Sauls who might one day become Pauls. They were not those backsliders, ineffectuals, who quietly drop away. These were contaminators and killers—they were what the Qur’án calls ‘the diseased of heart’.[76] ‘… guide into the torment of the Flame’, the Qur’án says of Satan, ‘whoever shall take him for his Lord.’[77] Satan, the dark side of man, will seize a soul, then cast him out, and tell him, ‘I cannot aid you, neither can ye aid me. I never believed that I was His [God’s] equal …’[78] Nor should anyone imagine that these persons are stupid: English has preserved a tribute to their mental powers in such expressions as ‘fiendish ingenuity’ and ‘diabolical intelligence’.
(Summon Up Remembrance by Marzieh Gail, Oxford: George Ronald, 1987)
https://bahai-library.com/pdf/g/gail_summon_up_remembrance.pdf