Mishkat al-Masabih 9 Supplications كتاب الدعوات 108

وَعَنْ جُنْدُبٍ رَضِيَ اللَّهُ عَنْهُ أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ حَدَّثَ: ” أَنَّ رَجُلًا قَالَ: وَاللَّهِ لَا يَغْفِرُ اللَّهُ لِفُلَانٍ وَأَنَّ اللَّهَ تَعَالَى قَالَ: مَنْ ذَا الَّذِي يَتَأَلَّى عَلَيَّ أَنِّي لَا أَغْفِرُ لِفُلَانٍ فَإِنِّي قَدْ غَفَرْتُ لِفُلَانٍ وَأَحْبَطْتُ عَمَلَكَ ” . أَوْ كَمَا قَالَ. رَوَاهُ مُسلم

Jundub said that God’s messenger told of a man saying, “I swear by God that God will not forgive so and so,” whereupon God most high said, “Who is this who swears that I will not forgive so and so? For I have forgiven so and so and have made your deeds to come to nothing”, or words to that effect. Muslim transmitted it.