بسم الله الرحمن الرحيم
And We have certainly established you upon the earth and made for you therein ways of livelihood. Little are you grateful. And We have certainly created you, [O Mankind], and given you [human] form. Then We said to the angels, “Prostrate to Adam”; so they prostrated, except for Iblees. He was not of those who prostrated. [ Allah ] said, “What prevented you from prostrating when I commanded you?” [Satan] said, “I am better than him. You created me from fire and created him from clay.” [ Allah ] said, “Descend from Paradise, for it is not for you to be arrogant therein. So get out; indeed, you are of the debased. [Satan] said, “Reprieve me until the Day they are resurrected.” [ Allah ] said, “Indeed, you are of those reprieved.” [Satan] said, “Because You have put me in error, I will surely sit in wait for them on Your straight path. Then I will come to them from before them and from behind them and on their right and on their left, and You will not find most of them grateful [to You].” [ Allah ] said, “Get out of Paradise, reproached and expelled. Whoever follows you among them – I will surely fill Hell with you, all together.” (Surat al-A’raf, 7:10-18)
Before Allah commences with the story of Iblis in this Surah, He reminds us that while He has made our livelihood for us, we are seldom grateful; then He turns to the story of Iblis. Iblis refuses to bow down to Adam, because he was arrogant. But he also refused to submit to Allah, who gave him everything; he was ungrateful. Those two reasons got him kicked out of Paradise; and he tries to keep us out of Paradise by ensuring that we are ungrateful to Allah.
It wasn’t that Iblis did not believe in Allah; he believes in Allah and His Oneness. But he reached the height of ingratitude and arrogance; that is true kufr.
And that is the lesson that we should take; how much arrogance do we have? How grateful are we to Allah and His blessings?