Az-Zumar 39:53

Say [Allah says], “O My slaves who have transgressed against themselves, do not despair of Allah’s mercy, for indeed Allah forgives all sins[15]. He is indeed the All-Forgiving, the Most Merciful.

[15] It is for those who repent and correct themselves, no matter how big the sins are. The only unforgivable sin in Islam is dying in disbelief in Allah or associating others with Him. See 4:48. The Prophet (ﷺ) reports that Allah Almighty says, "O children of Adam! As long as you call upon Me, putting your hope in Me, I will forgive you for what you have done, and I will not mind. O children of Adam! If your sins were to reach the clouds of the sky and then you sought My forgiveness, I would forgive you. O children of Adam! If you were to come to Me with sins filling the whole world and then you came to Me without associating partners with Me, I would certainly match your sins with forgiveness." [At-Tirmidhi]

Say, "O My servants who have transgressed against themselves [by sinning], do not despair of the mercy of Allāh. Indeed, Allāh forgives all sins.[1354] Indeed, it is He who is the Forgiving, the Merciful."

[1354] For those who repent and correct themselves.

53. Say: "O ‘Ibâdî (My slaves) who have transgressed against themselves (by committing evil deeds and sins)! Despair not of the Mercy of Allâh: verily, Allâh forgives all sins. Truly He is Oft-Forgiving, Most Merciful.[12]

[12] (V.39:53)
A) See the footnote of (V.9:121).
B) See the footnote of (V.22:27).
C) See the footnote of (V.25:70).

Say: O My slaves who have been prodigal to their own hurt! Despair not of the mercy of Allah, Who forgiveth all sins. Lo! He is the Forgiving, the Merciful.