‘Abdullah ibn ‘Amr ibn al-‘Aas رضي الله عنه narrated from the Prophet Muhammad صلى الله عليه و آله و سلم,
“Verily, Allah does not take knowledge by removing it from the breasts of men, rather he takes knowledge by taking the scholars [in death]; until when no scholar remains, people take the ignorant as their leaders, and ask them questions, while they pass verdicts without knowledge, and become astray and lead others astray.”
{Sahih Bukhari & Muslim}