Allah commanded us to be merciful, loving, and forgiving to one another. And He made this a quality in His Messenger so that we could follow Prophet Muhammed’s example
One of the biggest and evilest wreckers of this compassion, love and brotherhood is backbiting. The word in Arabic is Gheebah, coming from the root: Gha-Yaa-Baa, meaning that which is unseen. When a Muslim sees his brother or sister committing a sin, without advising them directly, they go to others and speak ill of them in their absence.
Backbiting is Haram, it is one of the major sins and repentance must be sought for this sin. There is no other opinion in Islam.In this audio file Muhammed Alshareef talks about the importance of holding one tongue.