All Muslims who are acquainted with the teachings of the Holy Qur’an are aware of the fact that Iblis (the devil) is the number one enemy of Allah (God), and that Allah has decreed him as being astray and cursed. As such, Iblis will never ask for forgiveness or repent to Allah, and he has only been granted a temporary respite until Judgment Day, when he along with his followers that he led astray shall be flung into the fire of Hell.
Allah Most High says to Iblis:
قَالَ فَاخۡرُجۡ مِنۡہَا فَاِنَّکَ رَجِیۡمٌ۞
وَّ اِنَّ عَلَیۡکَ اللَّعۡنَۃَ اِلٰی یَوۡمِ الدِّیۡنِ۞
Allah said: “Get out from here, for verily you are rejected. And upon you is the Curse until the Day of Judgment.” [Surah 15:34-35, see also Surah 38:77-78]
Allah furthermore states that He has already decreed and determined that Iblis and all those who follow him shall be damned to the fire of Hell. Hence, Iblis has no chance for repentance or salvation. His affair has already been determined. He has only been granted temporary respite in order to beguile people from the Straight Path. Iblis himself knows this, which is why he stated in the same dialogue:
قَالَ رَبِّ بِمَاۤ اَغۡوَیۡتَنِیۡ لَاُزَیِّنَنَّ لَہُمۡ فِی الۡاَرۡضِ وَ لَاُغۡوِیَنَّہُمۡ اَجۡمَعِیۡنَ۞
Iblis said: “My Lord, since You made me go astray, I swear that I shall beautify for them (evils) on the earth, and shall lead all of them astray.” (15:39)
Thus it becomes clear from the Holy Qur’an itself that Iblis is eternally damned and has no chance for repentance or salvation. His affair has already been determined and he himself is aware of it. Therefore, it is absolutely futile for Iblis to try to repent or worship Allah at this stage. Instead, Iblis himself has stated that so long as he is given respite he will do his utmost to lead mankind astray and have as many people join him in the blazing fire of Hell.
But the founder and Imam of the mushrik (pagan) Barelwi sect, Ahmad Reza Khan of Bareilly (1856-1921) mentions a fabricated story, under the heading of “Jinn becoming a Muslim”, that Iblis was once offering Salat with the intention of repenting to Allah and hoping for salvation:
ایک پہاڑ پر ابلیس نماز پڑھ رہا ہے میں نے اس کی یہ نئی بات دیکھ کر کہا کہ تیراکام تو نماز سے غافل کردینا ہے تو خود کیسے نماز پڑھتا ہے؟ اس نے کہاکہ شاید ربّ العزت تعالی میری نماز قبول فرمائے اور مجھےبخش دے۔
Translation: Iblis is offering Namaz [Salat] on a mountain. Seeing this new thing from him, I said: “Your job is to make people neglect prayers, but now you yourself are praying?!” He (Iblis) said: “Perhaps the Lord of Honor (Allah) Most High will accept my prayer and grant me salvation.”
Reference: Malfûzât Alâ Hadrat; part 1, p.64