1) Sadooq (r.a) has recorded in Oyoone Akhbaar that Imam Zadeh Hazrat Abdul Azeem the son of Abdullah Hassani said, "I heard from Abu Jafar the second, Imam Muhammad Taqi (A.S) who heard from his respected father Imam Rida (A.S) who quotes Imam Musa Kadhim (A.S) that he said: "A person by the name of Umroo bin Abeed entered into the presence of Abu Abdullah Imam Jafar Sadiq (A.S). After taking his seat he recited the following verse of the Qur’an:
﴾And those who shun the great sins and indecencies...﴿
The Holy Qur’an (Surah 42, The Consultations (Surah Shuara), verse37).
Then he (Umroo bin Abeed) paused.
"Why have you become silent?" asked the Imam (A.S),
"I would like to derive the Greater Sins from the Holy Qur’an." he replied.
The Imam said: "O Umroo, 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)...﴿
The Holy Qur’an (Surah 5, The Table spread with foods (Surah Maaidah), verse72).
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...﴿
The Holy Qur’an (Surah 12, The Prophet Joseph (Surah Yusuf), verse87).
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.﴿
The Holy Qur’an (Surah 7, The wall with Elevations (Surah Araaf), verse99).
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.﴿
The Holy Qur’an (Surah 19, Mary the mother of Jesus (Surah Maryam), verse14).
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 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.﴿
The Holy Qur’an (Surah 4, The Women (Surah Nisa) verse93).
6) To slander a believing man or a woman of adultery (or sodomy) is a Greater sin as is proved by the statement of Allah.
﴾Surely those who accuse chaste believing woman, unaware (of the evil), are cursed in this world and the hereafter, and they shall have a grievous chastisement.﴿
The Holy Qur’an (Surah 24, The light (Surah Nur) verse23).
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.﴿
The Holy Qur’an (Surah 4, The Women (Surah Nisa) verse10).
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.﴿
The Holy Qur’an (Surah 8, The Spoils of war (Surah Anfal) verse16).
9) One of the Greater Sins is to take "interest." 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.﴿
The Holy Qur’an (Surah 2, The Cow (Surah Baqarah) verse275).
[Explanation: Some people say that taking interest is same as any other business. But this verse clearly says that usury is different from trade. Secondly, usury is forbidden whereas trading is permitted.]
* The book named: GREATER SINS. By Al-Haaj Sayyed Abdul Hussein Dastghaib Shirazi (r.a)