Is the following hadith authentic? It has been recorded by Imam Muslim in his Sahih. It has been narrated on the authority of Abu Hurayra: A fornicator who fornicates is not a believer as long as he commits fornication, and no one who steals is a believer as long as he commits theft, and no one who drinks wine is a believer as long as he drinks it, and repentance may be accepted after that.
Does this mean if a Muslim drinks alcohol he is not a Muslim any more?
The Prophet (sws), we believe, intended to teach the believers that these sins negate our iman. When a person who professes belief in God and the related beliefs commits sins that means that at the time of committing sin he was not mindful of what his belief entailed. Had he fully conscious of his belief in that moment he would not have heeded to the desires of the flesh and would have stayed away from sin. Since his desires and other motives overcame him at that moment he was not in the conscious state of belief.
This also means that our iman is something that is at times more active and flourishing and at other times and situations it can be dormant and silent to the stage of zero. When we do righetous deeds and worship it is growing and when we give in to the desires of the flesh we lose our faith.
This however relates only to the true state of one's faith and has nothing to do with the legal aspect of one's religious affiliation. That is only dependent only on stating that one is a believer and fuflilling some apparant Muslim practices and rituals. Therefore, we cannot say that someone who commits zina or who drinks is out of folds of Islam.