In the Holy Qur'an

O you who believe! avoid most of suspicion, for surely suspicion in some cases is a sin, and do not spy nor let some of you backbite others. Does one of you like to eat the flesh of his dead brother? But you abhor it; and be careful of (your duty to) Allah, surely Allah is Oft-returning (to mercy), Merciful. (49:12)

In the Traditions

Imam Baqir said, "When my father Ali ibn al-Hussain was close to death he drew me to his chest saying, 'O son give you the same advices as my father gave me, just as his father had given him the same advice: bear the truth patiently, even if it is bitter."