A Muslim should steer clear of all sins, major and minor ones. A faithful Muslim takes care of every utterance or deed, avoiding anything that makes him subject to the punishment of Allah and His Wrath.
The major sins are those acts which have been forbidden by Allah in the Qur’an and by His Messenger (peace and blessings be upon him) in the Sunnah, and which have been made clear by the actions of the first righteous generation of Muslims, the Companions of the Prophet. Allah Almighty says: “If you avoid the major (part) of what you have been forbidden (to do), We will cancel out for you your (other) evil deeds and will admit you (to Paradise) with a noble entry.” (An-Nisaa’:31)
In this verse, Allah Almighty has guaranteed the Garden of Paradise to those who avoid the major sins. And Allah Almighty also says: “Those who avoid the greatest of sins and indecencies, and forgive when they are angry” (Ash-Shura: 37) and “Those who avoid the greatest sins and indecencies, except for oversights, (will find that) surely your Lord is ample in forgiveness.” (An-Najm: 32)
The Messenger of Allah (peace and blessings be upon him) said: “The five (daily) Prayers, Friday to Friday and Ramadan to Ramadan, make atonement for what has happened since the previous one, as long as major sins have been avoided.” It is therefore very important to determine exactly what the greatest vices, technically called “the major sins” (kaba’ir), are in order that Muslims should avoid them.
There is some difference of opinion among scholars in this regard. Some say these major sins are seven, and in support of their position they quote the hadith: “Avoid the seven noxious things: associating anything with Allah, magic, killing one whom Allah has declared inviolate without a just cause, consuming the property of an orphan, devouring riba (interest), turning back when the army advances, and slandering chaste women who are believers but indiscreet.” (Al-Bukhari and Muslim)
`Abdullah ibn `Abbas said: “Seventy is closer to their number than seven,” and indeed that is correct. The above hadith does not limit the major sins to those mentioned in it. Rather, it points to the type of sins which fall into the category of major. These include those crimes which call for a prescribed punishment (hadd), such as theft, fornication or adultery, and murder; those prohibited acts for which a warning of a severe punishment in the Hereafter is given in the Qur’an or the Sunnah; and also those deeds which are cursed by our Prophet (peace and blessings be upon him). These are all major sins.
Of course, there is a gradation among them, since some are more serious than others. We see that the Prophet (peace and blessings be upon him) has included shirk (associating someone or something with Allah) among them, and from the text of the Qur’an we know that a person who commits shirk will not be forgiven and will remain in Hell forever. Allah Most High says: “Surely, Allah does not forgive associating anything with Him, and He forgives whatever is other than that to whomever He wills.” (An-Nisaa’: 48)
The Major Sins
1. Associating anything with Allah
2. Murder
3. Practicing magic
4. Abandoning salah (ritual Prayer)
5. Not paying zakah
6. Not fasting during the month of Ramadan without excuse
7. Not performing Hajj, while being able to do so
8. Showing disrespect to parents
9. Severing relations with relatives
10. Committing adultery
11. Committing sodomy
12. Dealing in riba (interest)
13. Wrongfully consuming the property of an orphan
14. Lying about Allah or His Messenger
15. Running away from the battlefield
16. Deceiving the people that one rules and being unjust to them
17. Being proud and arrogant
18. Bearing false witness
19. Drinking alcohol
20.Gambling
21. Falsely accusing chaste women (i.e. of committing fornication or adultery)
22. Stealing from the spoils of war
23. Stealing
24. Committing highway robbery
25. Making false oath
26. Committing oppression
27. Earning ill-gotten gain.
28. Consuming what is unlawful.
29. Committing suicide
30. Lying frequently
31. Judging unjustly
32. Giving and accepting a bribe
33. Imitating the opposite sex (in dress, behavior, and the like)
34. Allowing one’s wife, daughters, etc. to display their beauty to men or conduct illicit sexual relations
35. Marrying a divorced woman in order to make her lawful for her ex-husband to remarry her after he irrevocably divorced her
36. Not protecting oneself or one’s clothes from being contaminated with urine or excrement.
37. Showing off
38. Learning knowledge of the religion for the sake of this world and withholding that knowledge (i.e., not teaching people)
39. Betraying a trust
40. Recounting favors
41. Denying Allah’s Decree
42. Listening to people’s private conversations
43. Carrying gossip
44. Swearing
45. Breaking contracts
46. Believing in fortune-tellers
47. Behaving badly towards one’s husband
48. Making statues
49. Lamenting, wailing, tearing the clothing, and doing other things of this sort when an affliction falls
50. Treating others wrongfully
51. Treating one’s wife, servant, the weak, and animals badly
52. Offending one’s neighbor
53. Offending and abusing Muslims
54. Offending people and having an arrogant attitude toward them
55. Trailing one’s garment in pride
56. Wearing silk and gold (this is for men only)
57. Running away from one’s master (this is for slaves)
58. Slaughtering an animal that has been dedicated to anyone other than Allah
59. To knowingly ascribe one’s paternity to a man other than one’s biological father
60. Arguing and disputing violently
61. Withholding excess water
62. Giving short weight or measure
63. Feeling secure from Allah’s Plan
64. Offending pious people
65. Not praying in congregation but praying alone without an excuse
66. Persistently missing Friday Prayer without any excuse
67. Usurping the rights of the heir through bequests (to others)
68. Deceiving and plotting evil
69. Spying for the enemy of the Muslims against Muslim’s interest
70. Cursing or insulting any of the Companions of the Prophet
Source: The Major Sins (Al-Kaba’ir) by Muhammad ibn `Uthman Adh-Dhahabi, rendered into English by Mohammad Moinuddin Siddiqui.