When Satan rejected the order of Allah
[Taken from Qur'anic verses from 71 to 85 of Surah Saad (38)]
Allah says: (Remember) when your Lord (Allah) said to the angels: "Truly, I am going to create man from clay". So when I have fashioned him and breathed into him (his) soul created by me, then you fall down, prostrate to him." So the angels prostrated themselves, all of them: Except Iblis (Satan). He was proud and was one of the disbelievers.
(Allah) said: "O Iblis (Satan)! What prevents you from prostrating yourself to one whom I have created with both My Hands? Are you too proud (to fall in prostration to Adam) or are you one of the highly exalted?"[Iblis (Satan)] said: "I am better than he, you created me from fire, and you created him from clay."(Allah) said: "Then get out from here, for verily, you are outcast." And verily! My Curse is on you till the Day of Recompense."
[Iblis (Satan)] said: "My Lord! Give me then respite till the Day the (dead) are resurrected."(Allah) said: "Verily! You are of those allowed respite "Till the Day of the time appointed."[Iblis (Satan)] said: "By Your Might, then I will surely mislead them all," Except Your chosen slaves amongst them (faithful, obedient, true believers of Islamic Monotheism)." (Allah) said: "The Truth is, and the Truth I say, that I will fill Hell with you [Iblis (Satan)] and those of them (mankind) that follow you, together."