Abdullah ibn Amr reported: The Messenger of Allah, peace and blessings be upon him, said, “Verily, one of the major sins is that a man curses his own parents.” It was said, “O Messenger of Allah, how can a man curse his own parents?” The Prophet said, “He insults the father of another man and then that man insults his father and his mother.”
Source: Ṣaḥīḥ al-Bukhārī 5628, Ṣaḥīḥ Muslim 90
Grade: Muttafaqun Alayhi (authenticity agreed upon) according to Al-Bukhari and Muslim
عَنْ عَبْدِ اللَّهِ بْنِ عَمْرٍو رَضِيَ اللَّهُ عَنْهُمَا قَالَ قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ إِنَّ مِنْ أَكْبَرِ الْكَبَائِرِ أَنْ يَلْعَنَ الرَّجُلُ وَالِدَيْهِ قِيلَ يَا رَسُولَ اللَّهِ وَكَيْفَ يَلْعَنُ الرَّجُلُ وَالِدَيْهِ قَالَ يَسُبُّ الرَّجُلُ أَبَا الرَّجُلِ فَيَسُبُّ أَبَاهُ وَيَسُبُّ أُمَّهُ
5628 صحيح البخاري كتاب الأدب باب لا يسب الرجل والديه
90 صحيح مسلم كتاب الإيمان باب بيان الكبائر وأكبرها