If you are sad, and pass a child who is laughing, the child, seeing your sad face, will cease to laugh, not knowing why.
(‘Abdu’l-Bahá, ‘Abdu’l-Bahá in London, p. 124)
If you put a leper in a room with healthy people, he cannot catch their health; on the contrary they are very likely to catch his horrible ailment.
(Shoghi Effendi, Lights of Guidance, p. 188)
One must protect and safeguard the blessed souls from the breaths and fatal spiritual diseases; otherwise violation, like the plague, will become a contagion and all will perish.
(‘Abdu’l-Bahá, Bahá’í World Faith, p. 437)