If you are an ignorant man, ...

If you are an ignorant man, you are acting wisely; but if you have had any education, you are behaving like a fool.
 Theophrastus

Quotes from the same author

Time is the most valuable thing a man can spend.
 Theophrastus
True friends visit us in prosperity only when invited, but in adversity they come without invitation.
 Theophrastus