. . . The believers are commanded to shun Covenant-breakers
for the same reason as healthy people do not associate with a person suffering
from a serious contagious illness. A contagiously sick person cannot catch
health from a thousand healthy people, but, on the contrary, he can infect them
with his illness. Therefore such a person is quarantined and only those few
people qualified to attend him do so. . . . Then, if he proves adamant he is
free to go his way, but the Bahá'ís must cease to have any association with him
until such time as he repents when, of course, he can be accepted back into the
community.
- The Universal House of Justice (Letter dated March 23, 1975, to an individual believer; compilation: Developing Distinctive Baha’i Communities, NSA of USA, 1998 edition)