Explanation of the major sins

It is narrated from Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "No fornicator, when he is engaged in the sin of fornication, is a (complete) believer at that moment; nor is any thief, at the moment he commits theft, a (complete) believer; nor does any plunderer openly plunder some valuable and great thing while people raise their eyes towards him (in amazement and longing) and remain a (complete) believer at the time of that plunder."
This hadith is sahih (authentic) in its basis, and its supporting reports are found in Sahih al-Bukhari (2475) and Sahih Muslim (57). What is meant is that at the time of committing these major sins a servant is deprived of the highest level of faith or the light of faith, though he does not leave the fold of Islam.

Wahb (may Allah have mercy on him) narrates: I asked Sayyiduna Jabir bin Abdullah (may Allah be pleased with them both): Did you hear the Prophet (peace and blessings be upon him) say: "The fornicator, when he fornicates, is not a (complete) believer, and the thief, when he steals, is not a (complete) believer"? He replied: "I did not hear it (directly) myself, but I was told that Sayyiduna Ibn Umar (may Allah be pleased with them both) used to narrate it."
This hadith is sahih (authentic), and it is also narrated in Sahih al-Bukhari (2475) and Sahih Muslim (57) through the chains of other Companions.

It is narrated from Sayyiduna Imran bin Husayn (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) asked (the Companions): "When you see a fornicator and a drinker of wine, what do you say about them?" They said: Allah and His Messenger know best. He (peace and blessings be upon him) said: "These acts are sheer indecencies, and (legal) punishment is prescribed for them. Shall I not tell you of the greatest of the major sins?" We said: Certainly, O Messenger of Allah! He (peace and blessings be upon him) said: "Associating partners with Allah, as Allah Almighty says: 'And whoever associates partners with Allah has certainly fabricated a tremendous sin' [Surah al-Nisa: 48]; and disobedience to parents. Then Allah, the Mighty and Majestic, said (mentioning them together with gratitude to Himself): 'Be grateful to Me and to your parents; to Me is the final return' [Surah Luqman: 14]." The narrator says: The Messenger of Allah (peace and blessings be upon him) had been reclining, then he (peace and blessings be upon him) sat up (to stress the gravity of the matter) and, warning repeatedly, said: "Beware! False speech; take heed! Lying (is also among the greatest sins)."
Imam al-Harith recorded this hadith in his Musnad (Bughyat al-Bahith: 699); its narrators are thiqat (trustworthy), but its chain is munqati' (broken) because al-Hasan al-Basri did not hear from Imran bin Husayn (may Allah be pleased with him); however, the text of the hadith is reliable on the basis of other authentic supporting reports.

It is narrated from Sayyiduna Abu Bakr al-Siddiq (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "It is (adopting the way of) disbelief in Allah Almighty for a person to attribute himself to a lineage (family) that is not (truly) known to be his; and it is disbelief in Allah Almighty to disown and disavow one's (real) lineage, however slight and obscure it may be."
The chain of this hadith contains a narrator named al-Sari bin Isma'il, who is da'if (weak) according to the hadith scholars; therefore its chain is da'if.

It is narrated from Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "Five kinds of people will not enter Paradise: the habitual drinker of wine, the one who severs ties of kinship, the one who believes in magic (that is, holds the effect of magic to be true), the one who hurts others by reminding them of his favours, and the soothsayer who tells of the unseen."
This narration is reported in Musnad Ahmad and Musnad Abi Ya'la; its chain is criticised because of the weakness of Atiyyah bin Sa'd al-Awfi, though the condemnation of the evils mentioned in it and the warning against them are also established by other authentic hadith and texts.

It is narrated from Sayyiduna Buraydah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever deceives a man concerning his family (that is, his wife) or his servant (by inciting or enticing them against him and corrupting them), he has nothing to do with us."
Layth bin Abi Sulaym in the chain of this hadith is da'if (weak), but on the basis of other supporting reports Allamah al-Albani (may Allah have mercy on him) and other researchers have declared its meaning to be sahih (authentic).

It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that he was asked about the major sins, and he said: "Everything that Allah Almighty has forbidden in the Qur'an is a major sin", and he also mentioned the glance (a forbidden look, such as looking at a non-mahram woman).
Imam Abu Ya'la recorded it in his Musnad, and all its narrators are thiqat (trustworthy).

It is narrated from Sayyiduna Abu Ayyub al-Ansari (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "There is no servant who worships Allah Almighty in such a way that he associates nothing with Him, regularly establishes prayer, pays zakah, fasts the month of Ramadan and avoids the major sins, except that he will certainly enter Paradise." It was asked: What are the major sins? He (peace and blessings be upon him) said: "Associating anyone with Allah Almighty, and killing a soul (unjustly)."
This hadith is sahih (authentic).