Q: What is the ruling on committing sins, particularly major sins? Does this affect one's faith?
A: Yes, this has a great effect on one's faith. Committing the grave sins such as Zina (sexual intercourse and/or adultery), drinking wine, killing unjustly, consuming Riba (usury), backbiting, talebearing, etc., has an impact on one's faith in the Oneness of Allah and believing in Him. It weakens one's faith, but a Muslim is not to be accused of Kufr (disbelief) for commiting any of these sins, as long as he does not consider them lawful.
AlKhawarij (Kharijites, a Muslim sect who rebelled against both `Ali bin Abi Talib and Mu'awiah bin Abi Sufyan to found their independent group, then denied the principles of the Sunnah and divided into various subsects) consider as Kafir Muslims who commit sins such as Zina, theft, being undutiful to parents and other major sins; even if such a person does not consider the act to be lawful. This is a great mistake on the part of Kharijites.
Ahl AlSunnah wal Jama`ah (those adhering to the Sunnah and the Muslim community) neither consider such a person a Kafir, nor believe that he will abide in the Hellfire forever. Rather, they view that the Iman (belief) and Tawhid (belief in the Oneness of Allah/ monotheism) of this person are incomplete. Such a person is not to be accused of committing major Kufr, but that their Iman (belief) is incomplete and weak.
Therefore, Allah legislated that the fornicator must be given one hundred lashes and exiled for a year if he or she is not married as Hadd (legal penalty). Allah also legislates that the intoxicated person is to be lashed and not to be executed. This also applies to a thief whose hand must be cut off and should not be executed. Had committing Zina, intoxication and robbery carried the ruling of major Kufr (disbelief), they would have been executed as the Prophet (peace be upon him) said: "Whoever (a Muslim) abandons their faith, is to be executed."(Related by AlBukhari (may Allah be merciful with him) in his Sahih [Authentic Hadith Book]).
This indicates that committing sins does not constitute Riddah (apostasy), but weakens and decreases one's faith. Thus, Allah legislated disciplining them by applying these prescribed penalties so that they may turn to their Lord in repentance and be deterred from committing what Allah (Glorified be He) has made unlawful.
The Mu`tazilah (a deviant Islamic sect claiming that those who commit major sins are in a state between belief and disbelief) view that the sinner is between two ranks and will
abide in the Hellfire forever if they die believing in this. This opinion contradicts AhlulSunnah walJama`ah (those adhering to the Sunnah and the Muslim community) and agrees with the Kharijites. Yet, both sects are wrong.
and whoever does this shall receive the punishment. The torment will be doubled to him on the Day of Resurrection, and he will abide therein in disgrace;
Thus, those who commit major sins will abide in the Hellfire temporarily unlike disbelievers who will abide therein forever. As for the polytheists, Allah (Glorified and Exalted be He) says inSurah AlBaqarah: Thus Allâh will show them their deeds as regrets for them. And they will never get out of the Fire.
InSurah AlMa'idah, Allah (Glorified be He) says:with regard to the unbelievers: They will long to get out of the Fire, but never will they get out therefrom; and theirs will be a lasting torment.