Jealousy consumeth the body and anger doth burn the liver: avoid these two as you would a lion.
(Bahá’u’lláh, The Compilation of Compilations vol. I, p. 460)
Petty bickerings and jealousies make one lose all the traces of spirituality, excommunicate a person from the divine company of the worthy ones, submerge one in the sea of phantasms, suffer one to become cold and pessimistic and throw him headlong into the depths of despair and helplessness! You must not listen to anyone speaking about another; because no sooner do you listen to one than you must listen to someone else, and thus the circle will be enlarged endlessly. Therefore, say to them: “O friends! Let us come together, forget all our self-thoughts and be in one accord, and cry at the top of our voices, ‘Ya-Bahá-El-Abhá!’
(‘Abdu’l-Bahá, “Star of the West,” Vol. V, No. 1, p. 6)
The black-hearted scoundrel who befooled and manipulated this vain and flaccid man with consummate skill and unyielding persistence was a certain Siyyid Muhammad, a native of Isfahan, notorious for his inordinate ambition, his blind obstinacy and uncontrollable jealousy. To him Bahá’u’lláh had later referred in the Kitáb-i-Aqdas as the one who had “led astray” Mirza Yahya, and stigmatized him, in one of His Tablets, as the “source of envy and the quintessence of mischief,” while ‘Abdu’l-Bahá had described the relationship existing between these two as that of “the sucking child” to the “much-prized breast” of its mother.
(Shoghi Effendi, God Passes By, p. 112-113)
The only way jealousy or petty attitudes can be overcome is by the love and tact of the teacher; these are not things that can be solved by a ‘ruling‘.
(Shoghi Effendi, Lights of Guidance, p. 88)
When some souls turn away from the love of God, there is no harm therein. Did not Judas Iscariot, the chief of the apostles, turn away on account of jealousy for Peter the apostle? Likewise, some people must necessarily turn away on account of jealousy for others.
(‘Abdu’l-Bahá, Tablets of ‘Abdu’l-Bahá v2, p. 290)