What is the ruling on one who commits a major sin? And is he a disbeliever or not a believer?

In Islamic law, a perpetrator of a major sin is called a fasiq (transgressor). Absolute faith is not negated from him, nor is he considered a disbeliever. Rather, his faith decreases in proportion to the sins he commits. What is mentioned in the religious texts describing some sins as kufr (disbelief) is understood to refer to minor kufr, which does not expel one from the fold of Islam. Thus, a fasiq milli (a transgressor who is still within the religion) is a disobedient Muslim from whom absolute faith is not negated, even if his faith has diminished due to his transgression. Kufr can be minor or major, and likewise hypocrisy (nifaq), polytheism (shirk (definition)), and injustice (dhulm). A perpetrator of a major sin is not a disbeliever; rather, he is a fasiq who deserves the threat (of punishment), and his affair is with Allah—if He wills, He may forgive him—based on His saying, the Almighty: "Indeed, Allah does not forgive association with Him, but He forgives what is less than that for whom He wills."