Imaam Maalik bin Anas 179 AH said,

لا تأخذ العلم من سفيه معلن بالسفه وإن كان أروى الناس

“Do not take knowledge from a fool who is known for his foolishness, even if he narrates more than anyone.”

Jaami lil Akhlaq ar-Rawi wa Adab as-Saami’ 1/139