Question: I have heard that there are certain minor sins and certain major ones in Islam. Please explain.
    Answer: A study of the Qur’an reveals that it regards three acts as major sins. 
 
    1. Shirk (polytheism) 
    2. Murder 
    3. Adultery 
 
    For example, while describing the qualities of believers in Surah Furqan, the Almighty says: 

Those who invoke not with Allah any other god nor slay such life as Allah has made sacred except when justified, nor commit fornication. He who commits any of these shall meet the fate of these sins. He shall face a gradually increasing penalty on the Day of Judgement, and shall dwell there in ignominy unless he repents, believes and does righteous deeds. Then Allah will change his evil deeds with righteous ones and Allah is most Forgiving and Ever Merciful. (25:68-70)

    Another thing which needs to be understood is that according to the Qur’an, minor sins become major as well if they begin to encircle a person’s life and become habitual for him.

Nay those who commit a sin and their sin surrounds them, they are companions of the Fire; therein shall they abide forever. (2:81)