Cursing a believer or calling accusing him of kufr (disbelief) is akin to murder

who was one of the companions of the tree (who gave the pledge of allegiance to the Prophet ﷺ underneath the tree at Ḥudaybiyyah) that the Messenger of Allah ﷺ said, "Whoever swears by a religion other than Islam then he is really so. A child of Adam is not bound to fulfill a vow to Allah about a thing which he does not possess."

"If someone commits suicide with anything in this world, he will be tortured with it on the Day of Resurrection. If somebody curses a believer then his sin will be as if he killed him. And whoever accuses a believer of kufr (disbelief) then it is as if he killed him."  

وَكَانَ مِنْ أَصْحَابِ الشَّجَرَةِ حَدَّثَهُ أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ: «مَنْ حَلَفَ عَلَى مِلَّةٍ غَيْرِ الإِسْلاَمِ فَهْوَ كَمَا قَالَ؛ وَلَيْسَ عَلَى ابْنِ آدَمَ نَذْرٌ فِيمَا لاَ يَمْلِكُ؛»

«وَمَنْ قَتَلَ نَفْسَهُ بِشَىْءٍ فِي الدُّنْيَا عُذِّبَ بِهِ يَوْمَ الْقِيَامَةِ؛ وَمَنْ لَعَنَ مُؤْمِنًا فَهْوَ كَقَتْلِهِ؛ وَمَنْ قَذَفَ مُؤْمِنًا بِكُفْرٍ فَهْوَ كَقَتْلِهِ۔»  

[Machine] "The Prophet ﷺ said, 'Cursing a believer is like killing him, and whoever kills himself with something in this world will be punished with it in the hereafter. It is not permissible for a Muslim to make a vow about something he does not possess. And whoever accuses a believer of disbelief, it is as if he has killed him. And whoever takes an oath to a religion other than Islam falsely, he is as he said.'"  

أَنَّ النَّبِيَّ ﷺ قَالَ لَعْنُ الْمُؤْمِنِ كَقَتْلِهِ وَمَنْ قَتَلَ نَفْسَهُ بِشَيْءٍ فِي الدُّنْيَا عُذِّبَ بِهِ فِي الْآخِرَةِ وَلَيْسَ عَلَى رَجُلٍ مُسْلِمٍ نَذْرٌ فِيمَا لَا يَمْلِكُ وَمَنْ رَمَى مُؤْمِنًا بِكُفْرٍ فَهُوَ كَقَتْلِهِ وَمَنْ حَلَفَ بِمِلَّةٍ سِوَى الْإِسْلَامِ كَاذِبًا فَهُوَ كَمَا قَالَ  

[Machine] The Messenger of Allah ﷺ said, "Cursing a believer is like killing them, and whoever insults a believer with disbelief, it is as if he has killed them. And whoever swears by a religion other than Islam, it is as he has stated. And whoever kills himself with something, he will be punished with it on the Day of Resurrection, and there is no vow for a servant concerning what he does not possess."  

قَالَ رَسُولُ اللهِ ﷺ «لَعْنُ الْمُؤْمِنِ كَقَتْلِهِ وَمَنْ قَذَفَ مُؤْمِنًا أَوْ مُؤْمِنَةً بِكُفْرٍ فَهُوَ كَقَتْلِهِ وَمَنْ حَلَفَ بِمِلَّةٍ غَيْرِ الْإِسْلَامِ فَهُوَ كَمَا قَالَ وَمَنْ قَتَلَ نَفْسَهُ بِشَيْءٍ عُذِّبَ بِهِ يَوْمَ الْقِيَامَةِ وَلَيْسَ لِلْعَبْدِ نَذْرٌ فِيمَا لَا يَمْلِكُ»  

[Machine] The Messenger of Allah ﷺ said, "There is no vow in something that one does not possess, and cursing a believer is like killing him. Whoever kills himself with something in this world will be punished with it on the Day of Judgment, and whoever swears by a religion other than Islam falsely, he is as he said. And whoever says to a believer, 'O disbeliever,' it is as if he has killed him."  

أَنَّ رَسُولَ اللهِ ﷺ قَالَ «لَا نَذْرَ فِيمَا لَا يَمْلِكُ وَلَعْنُ الْمُؤْمِنِ كَقَتْلِهِ وَمَنْ قَتَلَ نَفْسَهُ بِشَيْءٍ فِي الدُّنْيَا عُذِّبَ بِهِ يَوْمَ الْقِيَامَةِ وَمَنْ حَلَفَ بِمِلَّةٍ غَيْرِ الْإِسْلَامِ كَاذِبًا فَهُوَ كَمَا قَالَ وَمَنْ قَالَ لِمُؤْمِنٍ يَا كَافِرُ فَهُوَ كَقَتْلِهِ»  

"Whoever swears by a religion other than Islam, telling a lie, will be as he said, and whoever kills himself with something, he will be punished with it in the Hereafter, and there is no vow concerning that which a man does not possess." (Using translation from Nasāʾī 3813)   

أَنَّ رَسُولَ اللهِ ﷺ قَالَ «لَيْسَ عَلَى رَجُلٍ نَذْرٌ فِيمَا لَا يَمْلِكُ وَلَعُنُ الْمُؤْمِنِ كَقَتْلِهِ وَمَنْ قَتَلَ نَفْسَهُ بِشَيْءٍ فِي الدُّنْيَا عُذِّبَ بِهِ يَوْمَ الْقِيَامَةِ وَمَنْ حَلَفَ بِمِلَّةٍ سِوَى الْإِسْلَامِ كَاذِبًا فَهُوَ كَمَا قَالَ وَمَنْ قَذَفَ مُؤْمِنًا بِكُفْرٍ فَهُوَ كَقَتْلِهِ»  

"Whoever swears by a religion other than Islam, telling a lie, will be as he said, and whoever kills himself with something, he will be punished with it in the Hereafter, and there is no vow concerning that which a man does not possess." (Using translation from Nasāʾī 3813)   

قَالَ رَسُولُ اللهِ ﷺ «مَنْ حَلَفَ بِمِلَّةٍ غَيْرِ الْإِسْلَامِ كَاذِبًا فَهُوَ كَمَا قَالَ وَمَنْ قَتَلَ نَفْسَهُ بِشَيْءٍ عُذِّبَ بِهِ يَوْمَ الْقِيَامَةِ وَلَيْسَ عَلَى الرَّجُلِ نَذْرٌ فِيمَا لَا يَمْلِكُ وَلَعْنُ الْمُؤْمِنِ كَقَتْلِهِ وَمَنْ رَمَى مُؤْمِنًا بِكُفْرٍ فَهُوَ كَقَتْلِهِ»  

(who was one of the companions who gave the pledge of allegiance to the Prophet ﷺ underneath the tree (Al-Hudaibiya)) Messenger of Allah ﷺ said, "Whoever swears by a religion other than Islam (i.e. if somebody swears by saying that he is a non-Muslim e.g., a Jew or a Christian, etc.) in case he is telling a lie, he is really so if his oath is false, and a person is not bound to fulfill a vow about a thing which he does not possess. And if somebody commits suicide with anything in this world, he will be tortured with that very thing on the Day of Resurrection; And if somebody curses a believer, then his sin will be as if he murdered him; And whoever accuses a believer of Kufr (disbelief), then it is as if he killed him." (Using translation from Bukhārī 6047)  

أَنَّ رَسُولَ اللهِ ﷺ قَالَ «مَنْ حَلَفَ عَلَى مِلَّةٍ غَيْرِ الْإِسْلَامِ فَهُوَ كَمَا قَالَ وَلَيْسَ عَلَى ابْنِ آدَمَ نَذْرٌ فِيمَا لَا يَمْلِكُ وَمَنْ قَتَلَ نَفْسَهُ بِشَيْءٍ فِي الدُّنْيَا عُذِّبَ بِهِ يَوْمَ الْقِيَامَةِ وَمَنْ لَعَنَ مُؤْمِنًا فَهُوَ كَقَتْلِهِ وَمَنْ قَذَفَ مُؤْمِنًا بِكُفْرٍ فَهُوَ كَقَتْلِهِ»  

"لَيسَ عَلَى رَجُلٍ نَذْرٌ فِيما لا يَمْلِكُ، وَلَعْنُ الْمُؤْمِنِ كَقَتْلِهِ، وَمَنْ قَتَلَ نَفْسَه بِشَيْءٍ عُذِّبَ بِه يَوْمَ الْقِيامَة، وَمَنْ حَلَفَ بِمِلَّةٍ سِوَى الإِسْلامِ كَاذِبًا، فَهُوَ كَمَا قَال، وَمَنْ قَذَفَ مُؤمِنًا بِكُفْرٍ، فَهُوَ كَقَتْلِهِ".