Prophet Muhammad (peace be upon him) said: "He who sees something which should be kept hidden and conceals it will be like the one who has brought to life a girl buried alive (a pre-Islamic practice). - Sunan of Abu-Dawud, Hadith 2292
Narrated Abu Barzah al-Aslami رضي الله ﺗﻌﺎﻟﯽٰ عنه : The Prophet (peace be upon him) said: O community of people who believed by their tongue and belief did not enter their hearts, do not back-bite Muslims, and do not search for their faults, for if anyone searches for their faults, Allah will search for his fault, and if Allah searches for the fault of anyone, He disgraces him in his own house. -Sunan of Abu Dawud, Number 2283 (Tirmidhi also reported a similar Hadith)
Narrated Abu Huraira رضي الله ﺗﻌﺎﻟﯽٰ عنه: Allah's Apostle ﺻﻠﯽ الله ﺗﻌﺎﻟﯽٰ ﻋﻠﯿﮧ ﻭﺍٓﻟﮧ ﻭﺳﻠﻢ said, "Beware of suspicion, for it is the worst of false tales and don't look for the other's faults and don't spy and don't hate each other, and don't desert (cut your relations with) one another. O Allah's slaves, be brothers!" - Sahih Al Bukhari, Vol. 8 Number 717
(Imam Bukhari's Book of Manners 329)
Ibn 'Abbas رضي الله ﺗﻌﺎﻟﯽٰ عنه said on the verse of the Qur'an, "Nor defame one another" (49:11), "Do not spend your time finding fault with one another."
(Imam Bukhari's Book of Manners #330)
This type of behaviour is very detrimental to the Muslim unity yet it is very rife
-because we hate one another.
-because we have different aqeeda or belong to different Jamaat.