“A leader leads by example, whether he intends to or not” means that even a leader’s flaws (something not intended to be seen) are examples of leadership. The popular saying is usually attributed to “anonymous.”
 
“The leader sets the example whether he intends to or not!” is from Donald G. Krause’s book, The Way of the Leader (1997).
 
 
The Quote Garden
Quotations about Leadership
A leader leads by example, whether he intends to or not.  ~Author Unknown
 
Google Books
The Way of the Leader
By Donald G. Krause
New York, NY: Berkley Pub. Group
1997
Pg. 8:
The leader sets the example whether he intends to or not!
   
Google Books
Creating High Performance Software Development Teams
By Frank P. Ginac
Upper Saddle River, NJ: Prentice Hall PTR
2000
Pg. ?:
Every person in a position of leadership leads by example whether they want to or not.
   
Google Groups: alt.flame.hammer   
Magic
Jun 28 2000
(...)
“A leader leads by example, whether he intends to or not.”—Anon
     
Quoteland.com
enola_catori
Posted 07-26-02 11:57 PM
(...)
A leader leads by example, whether he intends to or not. ~Author Unknown
 
Google Books
The 100 Greatest Leadership Principles of All Time
By Leslie Pockell and Adrienne Avila
New York, NY: Warner Business Books
2007
Pg. ?:
A leader leads by example, whether he intends to or not.
Anonymous
   
Google Books
Awakened Mind:
One-Minute Wake Up Calls to a Bold and Mindful Life
By David Kundtz
San Francisco, CA: Conari Press
2009
Pg. 86:
A leader leads by example, whether he intends to or not.
—American Proverb
 
Google Books
Leading Small Groups with Purpose:
Everything You Need to Lead a Healthy Group
By Steve Gladen
Grand Rapids, MI: Baker Books
2012
Pg. 54:
A leader leads by example, whether he intends to or not.
Anonymous