Amr ibn Nufayl says: I heard the Imam Hussein (as) say: "The one you await (the Mahdi) will not appear until you say you are distanced from one another, until you spit in one another's faces and accuse one another of denial and until you curse one another." I asked, 'Then there is nothing auspicious at that time?' He replied: "All the auspiciousness is in that period. Our Qaim (The Mahdi) will appear and put an end to all that." (Sheikh Muhammad bin Ibrahim Nomani, al-Ghaybah al-Nomani, p. 241)

Umayra, daughter of Nufayl, relates: "I heard the daughter of Hasan say: "This matter you expect (the coming of Hazrat Mahdi [as]) will not happen until SOME OF YOU STAND FAR APART FROM OTHERS AND CURSE EACH OTHER. (Bihar Al-Anwar, Vol. 52, p. 211)

According to some accounts related from Abd-Allah Ibn Habala, Imam Jaffari Sadiq said:

"THIS [THE COMING OF HAZRAT MAHDI (AS)] WILL HAPPEN WHEN YOU SPIT IN ONE ANOTHER'S FACES. SUCH THAT YOU WILL CURSE ONE ANOTHER AND EVEN CALL ONE ANOTHER LIARS."
(Sheikh Muhammad bin Ibrahim Nomani, al-Ghaybah al-Nomani, p. 241)