Reference: Shaykh Ibn ‘Uthaymeen – Kitaabul-‘Ilm
The Shaykh (rahima-hullaah) mentions:
If backbiting of the layman ranks amongst the major sins, then backbiting of the scholar is much greater. This is because the effects of backbiting of the scholar does not rest at him only, rather it rests upon him and that which he possesses in knowledge of the Sharee’ah.