Sayyiduna Mu'adh bin Jabal (may Allah be pleased with him) narrates: I presented myself before the Prophet (peace and blessings be upon him) (the narrator is in doubt about one word here) while he (peace and blessings be upon him) was circumambulating the House. I asked: O Messenger of Allah! Who is the worst person? He (peace and blessings be upon him) said: O Allah! I ask You for forgiveness. (Then he (peace and blessings be upon him) addressed Sayyiduna Mu'adh (may Allah be pleased with him) and said:) Ask about good, and do not ask about evil! The worst of people are those who are the evil scholars among the people.
Al-Bazzar recorded it; its chain contains al-Khalil bin Murrah. Al-Bukhari (may Allah have mercy on him) says: He is munkar al-hadith (his narrations are rejected). Ibn Adi rejected al-Bukhari's (may Allah have mercy on him) statement, and Abu Zur'ah says: He is a righteous shaykh.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب العلم / 874