The first Shia Imam, Ali ibn Abitaleb (AS) was asked:

Who are those who backbite, and want always to talk behind others and they enjoy it? Imam Ali (AS) replied: The weak and feeble ones. Backbiting is the climax of the efforts by a feeble and weak person. A strong and determined person is ashamed of backbiting others and considers it a bad act, the habit of the weak people. A strong person is not ready to backbite or hear others backbiting the people. Imam Ali (AS) said: A strong and determined person, with a strong soul never backbites [1].

[1] Nahjul Balaghah, Wisdom 461.

Source: en.shafaqna.com