Jami` at-Tirmidhi 2636
جامع الترمذي#2636Sahihحَدَّثَنَا أَحْمَدُ بْنُ مَنِيعٍ، حَدَّثَنَا إِسْحَاقُ بْنُ يُوسُفَ الأَزْرَقُ، عَنْ هِشَامٍ الدَّسْتَوَائِيِّ، عَنْ يَحْيَى بْنِ أَبِي كَثِيرٍ، عَنْ أَبِي قِلاَبَةَ، عَنْ ثَابِتِ بْنِ الضَّحَّاكِ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " لَيْسَ عَلَى الْعَبْدِ نَذْرٌ فِيمَا لاَ يَمْلِكُ وَلاَعِنُ الْمُؤْمِنِ كَقَاتِلِهِ وَمَنْ قَذَفَ مُؤْمِنًا بِكُفْرٍ فَهُوَ كَقَاتِلِهِ وَمَنْ قَتَلَ نَفْسَهُ بِشَيْءٍ عَذَّبَهُ اللَّهُ بِمَا قَتَلَ بِهِ نَفْسَهُ يَوْمَ الْقِيَامَةِ " . وَفِي الْبَابِ عَنْ أَبِي ذَرٍّ وَابْنِ عُمَرَ . قَالَ أَبُو عِيسَى هَذَا حَدِيثٌ حَسَنٌ صَحِيحٌ .
Narrated Ad-Dhahak:that the Prophet (ﷺ) said: "It is not for a slave (of Allah) to vow about something he does not possess, and cursing a believer is like killing him, and whoever accuses a believer of disbelief, then it is like he has killed him, and whoever kills himself with something, then Allah will punish him with whatever he killed himself with on the Day of Judgement
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
In-book reference: 40:31