Imam Malik {May Allah Mercy of Allah be upon him} said:
“Knowledge is not to be taken from four types of people:
❶ A foolish person who openly acts foolish, even if he reports the most narrations;
❷ an adherent of bid’ah who calls to his desires;
❸ a person who lies, even if I don’t accuse him of lying in regard to Hadith; and
❹ a righteous and pious worshiper who does not accurately retain what he narrates.”
{Siyar A’lam an-Nubala’ ~ The Lives of the Noble Figures ~ Section on the Biography of Imam Malik}