TABARANI 1326:
from Thābit b. al-Ḍaḥḥāk —
The Prophet ﷺ said, "Whoever swears by a religion other than Islam (i.e. if he swears by saying that he is a non-Muslim in case he is telling a lie), then he is as he says if his oath is false 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." (Using translation from Bukhārī 6105)
الطبراني ١٣٢٦:
عن ثابت بن الضحاك —
عَنِ النَّبِيِّ ﷺ قَالَ «مَنْ حَلَفَ بِمِلَّةٍ غَيْرِ الْإِسْلَامِ كَاذِبًا فَهُوَ كَمَا قَالَ وَمَنْ قَتَلَ نَفْسَهُ بِشَيْءٍ عُذِّبَ بِهِ فِي نَارِ جَهَنَّمَ وَلَعْنُ الْمُؤْمِنِ كَقَتْلِهِ وَمَنْ رَمَى مُؤْمِنًا بِكُفْرٍ فَهُوَ كَقَتْلِهِ»
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