I consider it essential to mention here some details of the greatest sin which will not be forgiven by Allah. This unpardonable sin is "SHIRK".

"SHIRK" implies ascribing partners to Allah or ascribing divine attributes to others besides Allah and believing that the source of power, harm and blessings comes from another besides Allah.

Almighty Allah says.

"Verily, Allah forgives not that rivals should be set up in worship with Him but He forgives save that (anything else) to whom He pleases, and whoever sets up rivals in worship with Allah, he has indeed invented a tremendous sin." (Holy Qur'an (4:48).

Almighty Allah says:

"Then when the trumpet is blown there will be no kinship among them that Day, nor will they ask of one another: Then those whose scales (of good deeds) are heavy, these! they are the successful. And those whose scales are light, these are those who lose their souls; in Hell will they abide.

The fire will burn their faces and they will look grin with displaced lips therein. (It will be said) Were not My Verses (the Qur'an) recited to you and then you used to deny them?

They will say: Our Lord, our misfortune overwhelmed us and we were erring people:

Our Lord, bring us out of this; if ever we return (to evil) then indeed we shall be wrongdoers.

He will say: Remain you in it with ignominy and speak you not to Me!" Holy Qur'an (23:101-108)