أبْغَضُ الخَلائِقِ إلَى اللّهِ المُغْتابُ
He who backbites is the most abhorred creature by Allah.
Backbiting is a sin and is mentioned in the Holy Quran in the following translated verse:
O you who have believed, avoid much [negative] assumption. Indeed, some assumption is sin. And do not spy or backbite each other. Would one of you like to eat the flesh of his brother when dead? You would detest it.