Kumail ibn Ziyad narrated: Once I was with Amirul Mu’mineen (a) in the mosque of Kufa, and when we completed our late evening prayers (i.e. Isha), he took me by his hands and came out of the mosque. He did not say a word till we arrived at the rear part of Kufa. As he entered the desert, he heaved a sigh and said: "O Kumail, no doubt these hearts (i.e. minds) are containers, and the best of them are those who retain most. Remember from me what I say; people are of three categories: the learned men (of piety), the students on the path of salvation, and (the third one) the riffraff of the society, following every croak of the crows, bending as the wind blows; never benefiting from the light of knowledge, nor finding a refuge with a strong supporter.