Appears 25 times in the Quran. (Root: كفر)
  1. And believe in what I have revealed, verifying that which is with you, and be not the first to deny it, neither take a mean price in exchange for My communications; and Me, Me alone should you fear.

  2. Many of the followers of the Book wish that they could turn you back into unbelievers after your faith, out of envy from themselves, (even) after the truth has become manifest to them; but pardon and forgive, so that Allah should bring about His command; surely Allah has power over all things.

  3. Surely those who disbelieve and die while they are disbelievers, these it is on whom is the curse of Allah and the angels and men all;

  4. They ask you concerning the sacred month about fighting in it. Say: Fighting in it is a grave matter, and hindering (men) from Allah's way and denying Him, and (hindering men from) the Sacred Mosque and turning its people out of it, are still graver with Allah, and persecution is graver than slaughter; and they will not cease fighting with you until they turn you back from your religion, if they can; and whoever of you turns back from his religion, then he dies while an unbeliever-- these it is whose works shall go for nothing in this world and the hereafter, and they are the inmates of the fire; therein they shall abide.

  5. Surely, those who disbelieve and die while they are unbelievers, the earth full of gold shall not be accepted from one of them, though he should offer to ransom himself with it, these it is who shall have a painful chastisement, and they shall have no helpers.

  6. And repentance is not for those who go on doing evil deeds, until when death comes to one of them, he says: Surely now I repent; nor (for) those who die while they are unbelievers. These are they for whom We have prepared a painful chastisement.

  7. O you who believe! do not take for guardians those who take your religion for a mockery and a joke, from among those who were given the Book before you and the unbelievers; and be careful of (your duty to) Allah if you are believers.

  8. Allah has promised the hypocritical men and the hypocritical women and the unbelievers the fire of hell to abide therein; it is enough for them; and Allah has cursed them and they shall have lasting punishment.

  9. O Prophet! strive hard against the unbelievers and the hypocrites and be unyielding to them; and their abode is hell, and evil is the destination.

  10. It did not beseem the people of Medina and those round about them of the dwellers of the desert to remain behind the Messenger of Allah, nor should they desire (anything) for themselves in preference to him; this is because there afflicts them not thirst or fatigue or hunger in Allah's way, nor do they tread a path which enrages the unbelievers, nor do they attain from the enemy what they attain, but a good work is written down to them on account of it; surely Allah does not waste the reward of the doers of good;

  11. O you who believe! fight those of the unbelievers who are near to you and let them find in you hardness; and know that Allah is with those who guard (against evil).

  12. And those before them did indeed make plans, but all planning is Allah's; He knows what every soul earns, and the unbelievers shall come to know for whom is the (better) issue of the abode.

  13. And they serve besides Allah that which neither profits them nor causes them harm; and the unbeliever is a partisan against his Lord.

  14. Surely those who disbelieve and turn away from Allah's way, then they die while they are unbelievers, Allah will by no means forgive them.

  15. Muhammad is the Messenger of Allah, and those with him are firm of heart against the unbelievers, compassionate among themselves; you will see them bowing down, prostrating themselves, seeking grace from Allah and pleasure; their marks are in their faces because of the effect of prostration; that is their description in the Taurat and their description in the Injeel; like as seed-produce that puts forth its sprout, then strengthens it, so it becomes stout and stands firmly on its stem, delighting the sowers that He may enrage the unbelievers on account of them; Allah has promised those among them who believe and do good, forgiveness and a great reward.

  16. Know that this world's life is only sport and play and gaiety and boasting among yourselves, and a vying in the multiplication of wealth and children, like the rain, whose causing the vegetation to grow, pleases the husbandmen, then it withers away so that you will see it become yellow, then it becomes dried up and broken down; and in the hereafter is a severe chastisement and (also) forgiveness from Allah and (His) pleasure; and this world's life is naught but means of deception.

  17. O you who believe! when believing women come to you flying, then examine them; Allah knows best their faith; then if you find them to be believing women, do not send them back to the unbelievers, neither are these (women) lawful for them, nor are those (men) lawful for them, and give them what they have spent; and no blame attaches to you in marrying them when you give them their dowries; and hold not to the ties of marriage of unbelieving women, and ask for what you have spent, and kt them ask for what they have spent. That is Allah's judgment; He judges between you, and Allah is Knowing, Wise.

  18. And if anything (out of the dowries) of your wives has passed away from you to the unbelievers, then your turn comes, give to those whose wives have gone away the like of what they have spent, and be careful of (your duty to) Allah in Whom you believe.

  19. O you who believe! do not make friends with a people with whom Allah is wroth; indeed they despair of the hereafter as the unbelievers despair of those in tombs.

  20. He it is Who created you, but one of you is an unbeliever and another of you is a believer; and Allah sees what you do.

  21. O Prophet! strive hard against the unbelievers and the hypocrites, and be hard against them; and their abode is hell; and evil is the resort.

  22. Surely We have warned you of a chastisement near at hand: the day when man shall see what his two hands have sent before, and the unbeliever shall say: O! would that I were dust!

  23. These are they who are unbelievers, the wicked.

  24. So today those who believe shall laugh at the unbelievers;

  25. Surely the disbelievers are rewarded as they did.