He Used To Say: "A Boor Cannot Be Sin-Fearing, Nor Can An Ignoramus Be Pious. A Bashful Person Will Not Learn, Neither Can The Short-Tempered Teach; Nor Can Anyone Who Is Over-Occupied In Trade Become A Scholar. In A Place Where There Are No Men, Strive To Be A Man."
"Sin-fearing" does not refer to a fear of the punishment to be received for sinning, but to the fear of sin itself, the fear that one will do something that is against G-d's will. A boor - a person who has not cultivated and developed his personality - is not capable of such feelings.
(Likkutei Sichos, Vol. XVIII, p. 61)