Imām Al-Zuhrī said:

Verily, knowledge has calamities [that afflict it]. One of its calamities is when the scholar is left, until he goes away with his knowledge. Another calamity is forgetting [knowledge]. Yet another calamity is lying about [knowledge], and this is the worst type.

Ibn 'Abd Al-Barr, Jāmi' Bayān Al-'Ilm article 684