The greater sins mentioned in the Quran

Umar bin Ubaid Mutazali, who was the Imam of Mutazalite sect came to Imam Sadiq (a.s) one day and recited the following verse of the Quran: And those who shun the great sins and indecencies…[1] Then he (Amr Ibn Ubaid) paused. “Why have you become silent?” asked the Imam (a.s). “I would like you to derive the Greater Sins from the Holy Quran.” he replied. The Imam said, “O Amr, the Greatest of the Greater Sins is Shirk (to attribute partners) with Allah. The Almighty Allah says: Certainly whoever associates (others) with Allah, then Allah has forbidden to him the Garden (Paradise)…[2]
2) After this, is “to despair from the Mercy of Allah.” As the Almighty Allah says: Surely none despairs of Allah's mercy except the unbelieving people...[3]
3) Then, “not fearing the retribution of Allah.” The High and the Mighty Allah remarks: But none feels secure from Allah's plan except the people who shall perish.[4]
4) One of the Greater Sins is to disobey ones parents because the Glorified Allah has said: And dutiful to his parents, and he was not insolent, disobedient.[5]
Here the disobedience of the parents is considered a form of insolence or transgression.
5) To kill a believer is prohibited by Allah. Because Allah (A.J.) has informed: And whoever kills a believer intentionally, his punishment is Hell; he shall abide in it, and Allah will send His Wrath on him and curse him and prepare for him a painful chastisement.[6]
6) To slander a believing man or a woman of adultery (or sodomy) is a Greater sin as proved by this statement of Allah: Surely those who accuse chaste believing women, unaware (of the evil), are cursed in this world and the hereafter, and they shall have a grievous chastisement.[7]
7) The usurpation of an orphan's property is a Greater sin, as is clear from the following verse: (As for) those who swallow the property of the orphans unjustly, surely they only swallow fire into their bellies and they shall enter burning fire.[8]
8) It is a Greater sin to retreat from Jihad (Holy war) as the Divine verse says: And whoever shall turn his back to them on that day- unless he turn aside for the sake of fighting or withdraws to a company- then he, indeed becomes deserving of Allah's wrath, and his abode is Hell; and an evil destination shall it be.[9]
9) One of the Greater Sins is to take usury. Allah, the Almighty informs: One who swallows down usury cannot arise except as one whom Shaitan has prostrated by (his) touch does rise. This is because they say, trading is only like usury; and Allah has allowed trading and forbidden usury.[10]
10) And magic is a Greater sin. Thus Allah (A.J.) And certainly they know that he who bought it (the magic) should have no share of good in the hereafter and evil was the price for which they sold their souls; had they but known this.[11]
11) Among the Greater Sins is Adultery (fornication). Allah says in the Holy Quran: And they who do not call upon another god with Allah and do not slay a soul which Allah has forbidden except in the requirements of justice, and (who) do not commit fornication. And he who does this shall find a requital of sin. The punishment shall be doubled to him on the Day of Resurrection, and he shall abide therein in abasement.[12]
12) One of the Greater Sins is taking a false oath. Allah says regarding it: (As for) those who take a small price for the covenant of Allah and their own oaths-Surely they shall have no portion in the hereafter, and Allah will not speak to them, nor will He look upon them on the day of resurrection nor will He purify them, and they shall have a painful chastisement.[13]
13) Among the sins, which are specifically graded, as Greater is a sin of “betrayal of trust”, or to act unfaithfully. Allah the Greatest has informed thus: It is not [attributable] to any prophet that he would act unfaithfully [in regard to war booty]. And whoever betrays, [taking unlawfully], will come with what he took on the Day of Resurrection. Then will every soul be [fully] compensated for what it earned, and they will not be wronged. So is one who pursues the pleasure of Allah like one who brings upon himself the anger of Allah and whose refuge is Hell? And wretched is the destination.[14]
14) Failure to pay the Zakat is a Greater sin. Allah says regarding it: And (as for) those who hoard up gold and silver and do not spend it in Allah's ways, announce to them a painful chastisement.[15]
15) To bear a false witness is also a Greater sin. Allah says: …and avoid false words.[16]
16) Do not conceal evidence, as it is a Greater sin. Allah says: …and do not conceal testimony and whoever conceals it, his heart is surely sinful; and Allah knows what you do.[17]
17) Drinking of wine is a Greater sin. As it is prohibited by Allah in the following verse of the Holy Quran: They ask you about intoxicants and games of chance. Say: In both of them there is great sin and means of profit for men, and their sin is greater than their profit.[18]
18) To willfully avoid the prayers or failure to perform any obligatory religious act is a Greater sin. The Holy Prophet (S) says: One who willfully avoids the prayers is away from the protection of Allah and His Messenger.
20) Breaking an oath is also a Greater sin. Allah has stated: Who break the covenant of Allah after contracting it and sever that which Allah has ordered to be joined and cause corruption on earth. It is those who are the losers.[19]
21) To break ties with the relatives is one of the Greater Sins. In the Quranic verse quoted below, Allah says: and cut asunder what Allah has ordained…[20]

When Imam Ja'far as-Sadiq (a.s) concluded his tradition the narrator, Amr Ibn Ubaid rose up and while going out stopped and said, “Certainly, one who does not follow the guidance of the Imams (a.s) and gives his own opinion is doomed.”[21][22]

Footnotes:
[1] 42:37, وَالَّذِينَ يَجْتَنِبُونَ كَبَائِرَ‌ الْإِثْمِ وَالْفَوَاحِشَ
[2] 5:72, إِنَّهُ مَن يُشْرِ‌كْ بِاللَّـهِ فَقَدْ حَرَّ‌مَ اللَّـهُ عَلَيْهِ الْجَنَّةَ
[3] 12:87, إِنَّهُ لَا يَيْأَسُ مِن رَّ‌وْحِ اللَّـهِ إِلَّا الْقَوْمُ الْكَافِرُ‌ونَ
[4] 7:99, فَلَا يَأْمَنُ مَكْرَ‌ اللَّـهِ إِلَّا الْقَوْمُ الْخَاسِرُ‌ونَ
[5] 19:14, وَبَرًّ‌ا بِوَالِدَيْهِ وَلَمْ يَكُن جَبَّارً‌ا عَصِيًّا
[6] 4:93, وَمَن يَقْتُلْ مُؤْمِنًا مُّتَعَمِّدًا فَجَزَاؤُهُ جَهَنَّمُ خَالِدًا فِيهَا وَغَضِبَ اللَّـهُ عَلَيْهِ وَلَعَنَهُ وَأَعَدَّ لَهُ عَذَابًا عَظِيمًا
[7] 24:23, إِنَّ الَّذِينَ يَرْ‌مُونَ الْمُحْصَنَاتِ الْغَافِلَاتِ الْمُؤْمِنَاتِ لُعِنُوا فِي الدُّنْيَا وَالْآخِرَ‌ةِ وَلَهُمْ عَذَابٌ عَظِيمٌ
[8] 4:10, إِنَّ الَّذِينَ يَأْكُلُونَ أَمْوَالَ الْيَتَامَىٰ ظُلْمًا إِنَّمَا يَأْكُلُونَ فِي بُطُونِهِمْ نَارً‌ا ۖ وَسَيَصْلَوْنَ سَعِيرً‌ا
[9] 8:16, وَمَن يُوَلِّهِمْ يَوْمَئِذٍ دُبُرَ‌هُ إِلَّا مُتَحَرِّ‌فًا لِّقِتَالٍ أَوْ مُتَحَيِّزًا إِلَىٰ فِئَةٍ فَقَدْ بَاءَ بِغَضَبٍ مِّنَ اللَّـهِ وَمَأْوَاهُ جَهَنَّمُ وَبِئْسَ الْمَصِيرُ‌
[10] 2:275, الَّذِينَ يَأْكُلُونَ الرِّ‌بَا لَا يَقُومُونَ إِلَّا كَمَا يَقُومُ الَّذِي يَتَخَبَّطُهُ الشَّيْطَانُ مِنَ الْمَسِّ ذَٰلِكَ بِأَنَّهُمْ قَالُوا إِنَّمَا الْبَيْعُ مِثْلُ الرِّ‌بَا وَأَحَلَّ اللَّـهُ الْبَيْعَ وَحَرَّ‌مَ الرِّ‌بَا
[11] 2:102, وَلَقَدْ عَلِمُوا لَمَنِ اشْتَرَ‌اهُ مَا لَهُ فِي الْآخِرَ‌ةِ مِنْ خَلَاقٍ وَلَبِئْسَ مَا شَرَ‌وْا بِهِ أَنفُسَهُمْ لَوْ كَانُوا يَعْلَمُونَ
[12] 25:68-69, وَالَّذِينَ لَا يَدْعُونَ مَعَ اللَّـهِ إِلَـٰهًا آخَرَ‌ وَلَا يَقْتُلُونَ النَّفْسَ الَّتِي حَرَّ‌مَ اللَّـهُ إِلَّا بِالْحَقِّ وَلَا يَزْنُونَ وَمَن يَفْعَلْ ذَٰلِكَ يَلْقَ أَثَامًا يُضَاعَفْ لَهُ الْعَذَابُ يَوْمَ الْقِيَامَةِ وَيَخْلُدْ فِيهِ مُهَانًا
[13] 3:77, إِنَّ الَّذِينَ يَشْتَرُ‌ونَ بِعَهْدِ اللَّـهِ وَأَيْمَانِهِمْ ثَمَنًا قَلِيلًا أُولَـٰئِكَ لَا خَلَاقَ لَهُمْ فِي الْآخِرَ‌ةِ وَلَا يُكَلِّمُهُمُ اللَّـهُ وَلَا يَنظُرُ‌ إِلَيْهِمْ يَوْمَ الْقِيَامَةِ وَلَا يُزَكِّيهِمْ وَلَهُمْ عَذَابٌ أَلِيمٌ
[14] 3:161-162, وَمَا كَانَ لِنَبِيٍّ أَن يَغُلَّ وَمَن يَغْلُلْ يَأْتِ بِمَا غَلَّ يَوْمَ الْقِيَامَةِ ثُمَّ تُوَفَّىٰ كُلُّ نَفْسٍ مَّا كَسَبَتْ وَهُمْ لَا يُظْلَمُونَ أَفَمَنِ اتَّبَعَ رِ‌ضْوَانَ اللَّـهِ كَمَن بَاءَ بِسَخَطٍ مِّنَ اللَّـهِ وَمَأْوَاهُ جَهَنَّمُ وَبِئْسَ الْمَصِيرُ‌
[15] 9:34, وَالَّذِينَ يَكْنِزُونَ الذَّهَبَ وَالْفِضَّةَ وَلَا يُنفِقُونَهَا فِي سَبِيلِ اللَّـهِ فَبَشِّرْ‌هُم بِعَذَابٍ أَلِيمٍ
[16] 22:30, وَاجْتَنِبُوا قَوْلَ الزُّورِ‌
[17] 2:283, وَلَا تَكْتُمُوا الشَّهَادَةَ وَمَن يَكْتُمْهَا فَإِنَّهُ آثِمٌ قَلْبُهُ وَاللَّـهُ بِمَا تَعْمَلُونَ عَلِيمٌ
[18] 2:219, يَسْأَلُونَكَ عَنِ الْخَمْرِ‌ وَالْمَيْسِرِ‌ قُلْ فِيهِمَا إِثْمٌ كَبِيرٌ‌ وَمَنَافِعُ لِلنَّاسِ وَإِثْمُهُمَا أَكْبَرُ‌ مِن نَّفْعِهِمَا
[19] 2:27, الَّذِينَ يَنقُضُونَ عَهْدَ اللَّـهِ مِن بَعْدِ مِيثَاقِهِ وَيَقْطَعُونَ مَا أَمَرَ‌ اللَّـهُ بِهِ أَن يُوصَلَ وَيُفْسِدُونَ فِي الْأَرْ‌ضِ ۚ أُولَـٰئِكَ هُمُ الْخَاسِرُ‌ونَ
[20] 13:25, وَيَقْطَعُونَ مَا أَمَرَ‌ اللَّـهُ بِهِ أَن يُوصَلَ
[21] Al-Kafi, Vol. 2, pp. 285-287.
[22] http://www.al-islam.org/akhlaq-al-aimma-morals-manners-holy-imams-maulan...