388-311 BC, Greek Dramatist
As iron is eaten away by rust, so the envious are consumed by their own passion.
Antisthenes – [Envy]

Observe your enemies, for they first find out your faults.
Antisthenes – [Enemies]

Pay attention to your enemies for they are the first to discover your mistakes.
Antisthenes – [Enemies]

Serve your enemies for they first find out your faults
Antisthenes – [Enemies]

We must not contradict, but instruct him that contradicts us; for a madman is not cured by another running mad also.
Antisthenes – [Argument]