The Prophet ﷺ said: Faith prevented assassination. A believer should not assassinate.

عَنِ النَّبِيِّ ﷺ قَالَ الإِيمَانُ قَيَّدَ الْفَتْكَ لاَ يَفْتِكُ مُؤْمِنٌ

A man came to az-Zubair bin al-’Awwam ؓ and said: “Shall I kill ʿAli for you?” He said: “No; how can you kill him when he has the troops with him?” He said: “I will catch up with him and assassinate him.” He said: “No. The Messenger of Allah ﷺ said: Faith prohibits assassination; no believer should resort to that.” Al-Hasan said: A man came to az-Zubair bin al-ʿAwwam ؓ and said: “Shall I not kill ʿAli for you?” He said: “How can you kill him when he has people with him?” (and he narrated a similar report.)

لَا إِنَّ رَسُولَ اللهِ ﷺ قَالَ إِنَّ الْإِيمَانَ قَيَّدَ الْفَتْكَ لَا يَفْتِكُ مُؤْمِنٌ

[AI] The Messenger of Allah ﷺ said: "The believer is affable, and there is no good in one who is not affable or is not befriended."

قَالَ رَسُولُ اللهِ ﷺ الْمُؤْمِنُ مَأْلَفَةٌ وَلَا خَيْرَ فِيمَنْ لَا يَأْلَفُ وَلَا يُؤْلَفُ

A man came to az-Zubair bin al-’Awwam ؓ and said: “Shall I kill ʿAli for you?” He said: “No; how can you kill him when he has the troops with him?” He said: “I will catch up with him and assassinate him.” He said: “No. The Messenger of Allah ﷺ said: Faith prohibits assassination; no believer should resort to that.” Al-Hasan said: A man came to az-Zubair bin al-ʿAwwam ؓ and said: “Shall I not kill ʿAli for you?” He said: “How can you kill him when he has people with him?” (and he narrated a similar report.) (Using translation from Aḥmad 1426)

قَالَ رَسُولُ اللَّهِ ﷺ «لَا يَفْتِكُ الْمُؤْمِنُ الْإِيمَانُ قَيْدُ الْفَتْكِ»

[AI] The Messenger of Allah ﷺ said, "A believer is friendly and there is no good in one who is not friendly and does not seek friendship."

قَالَ رَسُولُ اللهِ ﷺ «الْمُؤْمِنُ مَأْلَفَةٌ وَلَا خَيْرَ فِيمَنْ لَا يَأْلَفُ وَلَا يُؤْلَفُ»

"لَيسَ فِي الإِسْلامِ إِيمَاءٌ وَلَا فَتْكٌ، إِنَّ الإِيمَانَ قَيدُ الفَتْكِ، وَالنَّبِيُّ لَا يُومِئُ".