1. Fatal Sin One: Shirk (Associating Partners) with Allaah
Which is to equalize other things with Allaah [the One that created you], and worship other things besides him such as stones, human beings, the sun, the moon, a prophet, a shaikh, a friend, a star, a king, or other things or human beings.
Allaah the exalted says :
Verily Allaah forgives not, that rivals should be set up with Him in worship but He forgives save that (anything else) to whom He pleases.
And Allaah the Exalted says :
Verily who-so-ever sets up rivals in worship with Allaah, then Allaah has forbidden Paradise for him, and the fire will be his abode.

2. Shirk, Murder, Magic Not paying Zakat and Abandoning the Prayer
Major Sins in Islam
Shirk, Murder, Magic Not paying Zakat and Abandoning the Prayer

3. And Allaah the Exalted says :
Verily! joining others in worship with Allaah is a great wrong indeed.
So, whoever associates anything with the Exalted and dies as a mushrik, he is a permanent adherent of Hell, and he who worships Allaah alone he is a permanent adherent of Paradise even if he is tortured.
The Prophet said : Shall I tell you the fatal sins? Shirk with Allaah the hadeeth.
He also said : Avoid the seven fatal sins he mentioned shirk as one of them.
He said in another hadeeth : Whoever leaves his Deen kill him. This is authentic hadeeth.

4. Fatal Sin Two : Murder Allaah the Exalted says :
And whoever kills a believer intentionally, his recompense is Hell, to abide therein, and the wrath and the curse of Allaah are upon him and a great punishment is prepared for him.
And the Exalted says :
And those who invoke not with Allaah any other god nor kill such life as Allaah has forbiden, except for just cause, nor commit illegal sexual intercourse - 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; Except those who repent, believe.

5. Also Allah says I
If any one killed a person - unless it be for murder or for spreading mischief in the land, it would be as if he killed all mankind.
And when the female (infant) buried alive, is questioned - (as the pagan Arabs used to do), for what sin she was killed.

6. And the Prophet said : Avoid the seven fatal sins
And the Prophet said : Avoid the seven fatal sins Murder is mentioned as one of them
The Prophet also said : If Muslims fight each other with swords, the killer and the one killed are both in Hell. It is, then said : O Prophet of Allaah! It is understood why the killer is in hell, but what about the one killed? The Prophet said : He was covet to kill his Muslim brother.
Also the Prophet said : A man is still in a wide scope of religious actions unless he murders. he also said : Don’t return Blasphemer after me, killing one another.
Ibn Buraidah said : the Prophet said : Killing a believer is greater to Allaah than the vanishing of the earth. Wording of al- Bukhaari He also said : The first thing that is judged between people is blood.
Also the Prophet said : Allaah forbade on me the one who kills a believer. He said this three times, and this is on the conditions of Muslim.

7. The Prophet also said : Every soul that is killed unjustly, part of its blood is on Adams first son since he was thefirst to commit murder. The Prophet also said : He who kills a warrior, will not smell the fragrance of Paradise, which is smelt with in a walk of forty years.
He who kills a soul, that has Allaahs and the Prophets protection - breaks Allaahs and His Prophets commitment, and will never smell the fragrance of Paradise which is smelled from a walk of forty years.
[at-Tirmidhee authenticated it.]
On the authority of Abee Huraira that the Prophet said : He who backs on murdering a believer with even a word, meets Allaah, with a despairer of Allaahs Mercy written between his eyes.
[narrated by Imaam Ahmad and Ibn Majah and in the Isnad Maqil.]
Mu’wayweeyah said he heard the Messenger of Allaah say : Allaah forgives every sin, but a man dies a blasphemer, or a man kills a believer intentionally.

8. Fatal Sin Three : Magic
It is a fatal sin because the magician is a blasphemer always.
Allah says :
But the devils disbelieved, teaching men magic.
And satan teaches man magic only to make him disbelieve in Allah.
Allah says about Harut and Marut :
But neither of those [Harut and Marut] taught any one (such things) without saying: we are only for trial, so disbelieve (by learning this magic from us). And from these (angels) people learn that by which they cause seperation between man and wife

9. The penalty specified for the magician is execution because he has disbelieved, or nearly so, in Allaah
The Prophet said :
Avoid the seven sins He mentioned magic as being one of them.
So, man should be prudent that he does not let himself get into such things that make him loose his life on earth and his life in the hereafter. It is transmitted that the Prophet said :
The penalty specified for the magician is a strike with the sword.
[The authentication is from the saying of Jundaab.]
Bajalah Ibn ‘Abdah said :
A letter came to me from ‘Umar a year before his death to kill every magician, whether man or woman.

10. On the authority of Abee Musaa may Allaah be pleased with him that the Prophet said
Three do not enter heaven : the alcoholic, the severer of the bonds of kinship, and the one who believes in magic.
[narrated by Ahmad in Musnad]
Narrated by Ibn Mas’ood : Claiming to know the unkown, amulets, and Tiwalahs are Shirk.
[Narrated by Ahmad and Abu Daawood.]

11. Fatal Sin Four: Leaving the Prayer
Allaah the Exalted says :
Then, there has succeeded them a posterity who have given up prayers and followed lusts. So they will be thrown in hell, except those who repent. the Ayaah.
And the Exalted says :
So, woe to the worshippers who delay their prayers from its stated fixed time, those who do good deeds only to be seen (of men), and refuse (to supply) even neighbourly needs.

12. Another verse: .
What has caused you to enter Hell? They will say : we were not of those who prayed.
The Prophet said : The commitment between us and the disbelievers] is prayer, he who leaves it is a blasphemer.
He said also : He who misses the prayer of the afternoon looses all his work. He said : He who leaves prayers intentionally is fre of Allaah’s covenant of protection.
Umar, said : He who misses prayers has no luck in Islaam.
Abu Huraira said :
The Prophet said : The first thing man is asked for at the Day of Judgement is prayers. If it is done properly, the man passes. And if it is not done well, he looses

13. Also the prophet said:
I was commanded to fight people till they cite that there is no god but Allaah, and Muhammad is His Messenger, and fulfill prayers, and pay Zakat, if they fufill these things, they will prevent their blood and money within the rights of Islaam, and Allaah will reckon them.
Abu Sa’id said that a man said to the Prophet, O Prophet of Allaah! Fear Allaah, The Prophet said : Woe unto you! Am I not the only one on earth who fears Allaah most? Khalid Ibn al-Waalid said : Shall I cut his neck with this sword? The Prophet answered : No, He may be one of those who pray for Allaah.
Umar said : The Prophet said : He who keeps not his fulfilling of prayers will have no light, nor salvation, nor proof. and at the Day of Judgement he will be placed with Karun, Fir’awn, Haman and with ‘Ubai Ibn Khalaf.

14. Fatal Sin Five: Not Paying Zakat
Allaah says :
And woe to those who join gods with Allaah, those who practise not regular charity and who even deny the Hereafter.*
Allaah says also :
They who hoard up gold and silver and spend them not in the Way of Allaah, announce unto them a painful torment On the Day of Judgement when that (hoarded up gold and silver) will be heated in the fire of hell, and with it will be branded their foreheads, their flanks, and their backs - This is the treasure which you hoarded for yourselves : Now taste of what you used to hoard.

15. This process will continue functioning till the Day of Judgement.
The Prophet said : Any camel, or cow, or goat owner who does not pay zakat will be thrown down on his face on a hard land and for these [animals] to thrust him with its horns and step on him with its limbs, no sooner the last one steps and thrusts but the first one comes and repeats the action once again.
This process will continue functioning till the Day of Judgement.
Abu Bakr, fought those who did not pay zakaat and he said : I swear with Allaah, I will fight them for even a node they used to pay for the Prophet of Allaah and refuse to pay it now.

16. The Prophet Said:
He who refuses to pay Zakaat, we will take it from him and part of his camels (wealth) as a strict order from Allaah. Abu Huraira said : The Prophet said :
The first three people who go to Hell are : a prince who deals high - handedly with his subjects, a wealth owner who does not pay Zakaat, and a proud poor man.
Abdullaah says : You were commanded to pay Zakaat and pray. He who does not pay Zakaat his prayers will not be accepted.