And the third way of disbelief is ingratitude to the bounties (of Allah)...

And the third way of disbelief is ingratitude to the bounties (of Allah); and it is as Allah says quoting (the Prophet) Sulayman: “This is of the grace of my Lord that He may try me whether I am grateful or ungrateful; and whoever is grateful, he is grate­ful only for his own self, and whoever is ungrateful, then surely my Lord is Self-sufficient, Honoured “ (27:40); If you are grateful **,** I would certainly give you more, and if you are ungrateful, My chastisement is truly severe (14:7).

Therefore remember Me, I will remember you, and be thankful to Me, and do not be ungrateful to Me (2:152). (In all these verses Allah has used the word al-kufr = disbelief, to denote ungratefulness, and in­gratitude.) And the fourth way of disbelief is leaving out or neglecting what Allah has ordered to do. It is as Allah says: And when We made a covenant with you: You shall not shed your blood and you shall not turn your people out of your cities; then you gave a promise while you witnessed.

Yet you it is who slay your people and turn a party from among you out of their homes, backing each other up against them unlawfully and exceeding the limits; and if they should come to you as captives, you would ransom them - while their very turning out was unlawful for you. Do you then believe in a part of the book and disbelieve in the other? (2:84-85) .

In this verse Allah has charged them with disbelief because they did not follow the commandment of Allah; (it should be noted that) Allah has (in this very verse) linked them to belief, yet He did not accept it from them and it did not benefit them before Allah.

So Allah (further) said: What then is the reward of such among you as do this but disgrace in the life of this world, and on the day of resurrection they shall be sent back to the most grievous chastisement, and Allah is not at all heedless of what you do (ibid.) And the fifth way of disbelief is disavowal. It is as Allah says, quoting lbrahim (a.s.) “. . .

we renounce you, and enmity and hatred have appeared between us and you for ever until you believe in Allah alone” (60:4), that is, we disavow and repudiate you. And He says, describing Iblīs and his disowning his friends from mankind on the Day of Resurrection: “. . . surely I dis­believed in your associating me (with Allah) before” (14:22).