Jundub reported that Allah's Messenger (ﷺ) stated that a person said:
Allah would not forgive such and such (person). Thereupon Allah the Exalted and Glorious, said: Who is he who adjures about Me that I would not grant pardon to so and so; I have granted pardon to so and so and blotted out his deeds (who took an oath that I would not grant pardon to him).
حَدَّثَنَا سُوَيْدُ بْنُ سَعِيدٍ، عَنْ مُعْتَمِرِ بْنِ سُلَيْمَانَ، عَنْ أَبِيهِ، حَدَّثَنَا أَبُو عِمْرَانَ الْجَوْنِيُّ، عَنْ جُنْدَبٍ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم حَدَّثَ
أَنَّ رَجُلاً قَالَ وَاللَّهِ لاَ يَغْفِرُ اللَّهُ لِفُلاَنٍ وَإِنَّ اللَّهَ تَعَالَى قَالَ مَنْ ذَا الَّذِي يَتَأَلَّى عَلَىَّ أَنْ لاَ أَغْفِرَ لِفُلاَنٍ فَإِنِّي قَدْ غَفَرْتُ لِفُلاَنٍ وَأَحْبَطْتُ عَمَلَكَ
. أَوْ كَمَا قَالَ .