Generally we define sin as a wrong act. This wrong act can be committed in thoughts, in words or action. Therefore people like thieves, murderers, cheats would commonly be considered as sinners.
Sikh Concept of Sin
The concept of Sin in the Granth.
It is rather difficult to find a clear-cut definition of Sin in the Granth, though the Gurus prayed for the forgiveness of their sins and admitted that sin separates man from God.
Haumai is the most commonly used word which can be translated as sin. Haumai is associated with ego (self-centeredness), the natural condition that is inherent in manmukh (self-willed peson who disobeys God), and contrasted with Gurmukh (one who hears, and obey the Guru’s word).
It is Haumai which, through its willful attachment to Maya (or mohini), produces five evil passions called the demon; kam (lust), krodh (wrath), lobh (greed), moh (attachment to worldly things) and hanker (pride). SSGS pg 1219
These passions in turn result in violence, falsehood and doubt, producing evil deeds (karma) that bind manmukh (self-willed person) to the never ending cycle of transmigration of the soul, with its suffering and pain through repeated births and deaths. (Sri Guru Granth discovered, pg 77)
The Gurus and Sin
“My sins are as innumerable as the water when the seas and ocean are filled. Show mercy and extend a little pity and float me, a sinking stone.” (Guru Nanak, pg 156/2/523)
“I am a sinner without merit, O my master, shows goodness unto me.’ (Guru Nanak, pg 228/2/754)
“I am not soiled by one sin, that I may be washed clean with virtue alone.’ (Guru Nanak, pg 356/3/1189)
“I commit many sins O Lord, of which there is no limit. O God mercifully pardon me; I am a sinner and a greart offender.’ (Guru Amar Das, third guru, pg 1416/8/4680)
“O God, bless me with the dust of the feet of the perfect Guru that I, the sinner, may be emancipated.” (Guru Amar Das, third guru, pg 772/5/2516)
“My Lord, show such mercy unto me that my sins may be burnt away in an instant.’ ( Guru Ram Das, fourth guru, pg 1325/8/4374)
“Hearken to my supplications, O my Lord and master. I am full of millions of sins, nevertheless, I am thy slave.‘ (Guru Arjan Dev, fifth guru, pg 547/4/1798)
The above statements spoken by the Sikh Gurus are cries of despair, the lost searching for the Truth to cleanse them of their sins. These cries of the gurus echo the cries of mankind in the strugge with sin. They identified with the hunger which is inherited in all mankind that is to get rid of sin.