Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
quran:9:80 –

Ask forgiveness for them, ˹O Muhammad˺, or do not ask forgiveness for them. If you should ask forgiveness for them seventy times - never will Allah forgive them. That is because they disbelieved in Allah and His Messenger, and Allah does not guide the defiantly disobedient people.  

Ask forgiveness for them, O Muhammad (s), or do not ask forgiveness for them: this leaves the choice of asking forgiveness, or refraining, up to him; the Prophet (s) said, ‘I have been given the choice, and I made it’, meaning ˹the choice˺ to ask forgiveness, as reported by al-Bukhārī. If you ask forgiveness for them seventy times, God will not forgive them: it is said that the ‘seventy’ is intended to express ˹by hyperbole˺ a great frequency of asking forgiveness. In ˹the Sahīh of˺ al-Bukhārī there is a hadīth ˹which states˺: ‘If I was sure that were I to ask more than seventy times, God would forgive ˹them˺, I would have done so’. It is also said, however, that the very number ˹seventy˺ is actually meant, on account of this other hadīth of his: ‘I shall ask more than seventy times’, whereupon it was made clear to him ˹the Prophet˺ that the matter regarding forgiveness had been concluded by the verse, ˹Q. 63:6˺ Alike it will be regarding them: whether you ask forgiveness for them or you do not ask forgiveness for them ˹God will not forgive them˺; that is because they disbelieved in God and His Messenger; and God does not guide the wicked folk.
القرآن:٩:٨٠ –

اسْتَغْفِرْ لَهُمْ أَوْ لَا تَسْتَغْفِرْ لَهُمْ إِنْ تَسْتَغْفِرْ لَهُمْ سَبْعِينَ مَرَّةً فَلَنْ يَغْفِرَ اللَّهُ لَهُمْ ۚ ذَٰلِكَ بِأَنَّهُمْ كَفَرُوا بِاللَّهِ وَرَسُولِهِ ۗ وَاللَّهُ لَا يَهْدِي الْقَوْمَ الْفَاسِقِينَ  

(استغفر) يا محمد (لهم أو لا تستغفر لهم) تخيير له في الاستغفار وتركه قال ﷺ : "" إني خيرت فاخترت يعني الاستغفار "" رواه البخاري (إن تستغفر لهم سبعين مرة فلن يغفر الله لهم) قيل المراد بالسبعين المبالغة في كثرة الاستغفار وفي البخاري حديث "" لو أعلم أني لو زدت على السبعين غفر لزدت عليها "" وقيل المراد العدد المخصوص لحديثه أيضاً "" وسأزيد على السبعين "" فبين له حسم المغفرة بآية [سواء عليهم استغفرت لهم أم لم تستغفر لهم] (ذلك بأنهم كفروا بالله ورسوله والله لا يهدي القوم الفاسقين).

See similar narrations below:

Collected by Qurʾān, Suyūṭī
quran:63:6 –

It is all the same for them whether you ask forgiveness for them or do not ask forgiveness for them; never will Allah forgive them. Indeed, Allah does not guide the defiantly disobedient people.  

It will be the same for them, whether you ask forgiveness for them (a’staghfarta: the interrogative hamza here has taken the place of the conjunctive hamza) or do not ask forgiveness for them: God will never forgive them. Indeed God does not guide the immoral folk.
القرآن:٦٣:٦ –

سَوَاءٌ عَلَيْهِمْ أَسْتَغْفَرْتَ لَهُمْ أَمْ لَمْ تَسْتَغْفِرْ لَهُمْ لَنْ يَغْفِرَ اللَّهُ لَهُمْ ۚ إِنَّ اللَّهَ لَا يَهْدِي الْقَوْمَ الْفَاسِقِينَ  

{سواء عليهم أستغفرت لهم} استغني بهمزة الاستفهام عن همزة الوصل {أم لم تستغفر لهم لن يغفر الله لهم إن الله لا يهدي القوم الفاسقين}.
suyuti:804a –
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السيوطي:٨٠٤a –

"أخِّر عنى يا عُمَر، إنى خُيِّرتُ فاخترت، قد قيل لى: (استغفر لهم أو لا تستغفر لهم، إن تستغفر لهم سبعين مرةً فلن يغفرَ الله لهم) لو أعلمُ أنى لو زِدْتُ على السبعين غُفِر له لَزَدْت.  

[ت] الترمذي حسن صحيح غريب، [ن] النسائي عن عمر