Umar bin Khattab (razi Allah anhu) was an integrated man of dignity, discipline and truth. His life is full of lessons of personal and public leadership. He never relied on the external appearances of people and encouraged character ethic over personality ethic (as explained by Dr. Stephen Covey in 7 habits book)
At one occasion, he said: “Don’t be astonished by a person’s style (way of speaking, writing, expressing oneself). Real man in true sense is the one who keeps his promise and protect the dignity of others.” 
In the darkness of external appearances, hearts of men have landed in ashes, where a man is judged by the cars he keeps, the jeans he wear, the place he live and the language he speaks. Living in the modern, rather a virtual age, reality have limited itself to Batman, Superman and even Spiderman, but the real men have lost somewhere in the middle.
At another place Umar bin Khattab (razi Allah anhu) said, “Do not look at a man’s prayer and his fast, rather observe his intelligence and truthfulness” 
And he said, “I have no fear regarding two type of men among you;
1. an open believer,
2. an open disbeliever.
But I fear that hypocrite who hides himself in belief and does illegitimate acts” 
In Umar bin Khattab’s (razi Allah anhu) eyes, real man was the one who posses strong character traits like truthfulness, promise keeping, intelligence and honesty. We live in a world where we can’t trust anyone, people who are supposed to be upholders of truth utter great lies in front of everyone. We live in a world where personality is more important than character. It doesn’t fill up the inner hollowness while we find shortcuts to personal and public leadership.
The real deal is what is INSIDE and NOT what is OUTSIDE.
Once Umar bin Khattab inquired a man who came to stand as a witness for someone. Umar asked everyone, ” Is this man worth of standing as a witness?” A man among the people said, “I guarantee him being the witness.”
Umar (razi Allah anhu) asked this man, “are you his neighbour?” He replied no.
Umar (razi Allah anhu) asked, “Did you ever spent a single say with this man so that you know his reality?” He replied no.
Umar (razi Allah anhu) said, “you probably have just seen him praying in the mosque, isn’t it?” He said yes.
Umar said, “go away as you don’t know him then”.
These are the pricinples that Umar bin Khattab (razi Allah anh) used to determine someone’s character. It is much needed for us Muslims in today’s world as we have a great responsibility on our shoulders. We must strive to attain these qualities and learn lessons from the history.
O you who have believed, be persistently standing firm in justice, witnesses for Allah , even if it be against yourselves or parents and relatives. Whether one is rich or poor, Allah is more worthy of both. 
 Biography of Umar bin Khattab (razi Allahu anh) pg. 337, published by Darrusalam International publications
 Biography of Umar bin Khattab (razi Allahu anh) pg. 338, published by Darrusalam International publications
 Al Quran, Surah Nisa 4: Ayah 35