A knowledgeable person is not he who knows the good and the bad. Rather a knowledgeable person is he who knows the good and follows it; and he knows the evil and shuns it.

Abu Ma`mar al-Hudhlee reported on the authority of Sufyaan bin `Uyainah رحمه الله: [Tahdheeb Al-Kamaal by Al-Mizzee (11/191-192)]