Narrated Thabit bin Ad-Dahhak:The Prophet (ﷺ) said, "Whoever swears by a religion other than Islam, is, as he says; and whoever commits suicide with something, will be punished with the same thing in the (Hell) Fire; and cursing a believer is like murdering him; and whoever accuses a believer of disbelief, then it is as if he had killed him."
حَدَّثَنَا مُعَلَّى بْنُ أَسَدٍ، حَدَّثَنَا وُهَيْبٌ، عَنْ أَيُّوبَ، عَنْ أَبِي قِلاَبَةَ، عَنْ ثَابِتِ بْنِ الضَّحَّاكِ، قَالَ قَالَ النَّبِيُّ صلى الله عليه وسلم " مَنْ حَلَفَ بِغَيْرِ مِلَّةِ الإِسْلاَمِ فَهْوَ كَمَا قَالَ ـ قَالَ ـ وَمَنْ قَتَلَ نَفْسَهُ بِشَىْءٍ عُذِّبَ بِهِ فِي نَارِ جَهَنَّمَ، وَلَعْنُ الْمُؤْمِنِ كَقَتْلِهِ، وَمَنْ رَمَى مُؤْمِنًا بِكُفْرٍ فَهْوَ كَقَتْلِهِ ".
Bukhari
Oaths and Vows • Hadith 31