This story is taken from Mahabharata

Once Bhagwan Sh. Krishan and Bhishm designed a ‘test.
They called in Duryodhan one early morning and asked him to go around a kingdom for the whole day and return when he finds a ‘good person’ or by sunset, whichever is earlier.
A few minutes later they called in Yudhishthir and asked him to go around the entire kingdom for the whole day and return when he finds ‘an evil person’ or by sunset, whichever is earlier.
In the evening, Duryodhan returned empty handed and said that he could not find a single good person in the entire kingdom.
Yudhishthir also returned empty handed and said that he could not find a single evil person in the entire kingdom.

Bhagwan Sh. Krishan explained that because Duryodhan is evil from inside so whichever person meet him, he think he is evil on the other hand Yudhisthir is good from inside so he couldn't find any evil outside.

Moral:
The outside is the reflection of my inside.