November 30. On this date in 1944, a letter written on behalf of Shoghi Effendi to an individual believer compares Covenant-breakers to "a contagious spiritual disease," "a cancer," and "a poison." "Bahá'u'lláh and the Master in many places and very emphatically have told us to shun entirely all Covenant-breakers as they are afflicted with what we might try and define as a contagious spiritual disease...Also, it has nothing to do with unity in the Cause; if a man cuts a cancer out of his body to preserve his health and very life, no one would suggest that for the sake of unity it should be reintroduced into the otherwise healthy organism. On the contrary, what was once a part of him has so radically changed as to have become a poison."

November 30. On this date in 1944, a letter written on behalf of Shoghi Effendi to an individual believer compares Covenant-breakers to "a contagious spiritual disease," "a cancer," and "a poison." "Bahá'u'lláh and the Master in many places and very emphatically have told us to shun entirely all Covenant-breakers as they are afflicted with what we might try and define as a contagious spiritual disease...Also, it has nothing to do with unity in the Cause; if a man cuts a cancer out of his body to preserve his health and very life, no one would suggest that for the sake of unity it should be reintroduced into the otherwise healthy organism. On the contrary, what was once a part of him has so radically changed as to have become a poison."

604. Afflicted with Contagious Spiritual Disease
"Regarding Mr. ... question about the Covenant-breakers, Bahá'u'lláh and the Master in many places and very emphatically have told us to shun entirely all Covenant-breakers as they are afflicted with what we might try and define as a contagious spiritual disease; they have also told us, however, to pray for them. These souls are not lost forever. In the Aqdas, Bahá'u'lláh says that God will forgive Mirza Yahya if he repents. It follows, therefore, that God will forgive any soul if he repents. Most of them don't want to repent, unfortunately. If the leaders can be forgiven it goes without saying that their followers can also be forgiven.
"Also, it has nothing to do with unity in the Cause; if a man cuts a cancer out of his body to preserve his health and very life, no one would suggest that for the sake of unity it should be reintroduced into the otherwise healthy organism. On the contrary, what was once a part of him has so radically changed as to have become a poison."
(From a letter written on behalf of the Guardian to an individual believer, November 30, 1944: Principles of Bahá'í Administration, pp. 22-23)