Doubt is the key to knowledge.
More Persian Proverbs:
You can't take blood from a stone.Persian
You only appreciate your father the day you become a father yourself.
Persian
The hand that gives is also the one that receives.
Persian
Bribery makes both parties happy.
Persian
Doubtful the die, and dire the cast!
Persian
If you fall into a pit, Providence is under no obligation to come and look for you.
Persian