We were along with Messenger of Allah ﷺ in an expedition that a person from amongst the emigrants struck at the back of a person from the Ansir. The Ansiri said: O Ansar! And the Muhijir said: O Emigrants! Thereupon Messenger of Allah ﷺ said: What are these proclamations of the Days of Ignorance? They said: Messenger of Allah, a person from the emigrants struck at the back of an Ansari, whereupon he said: It is something disgusting. 'Abdullah b. Ubayy heard it and said: They have indeed done it. By Allah, when we would return to Medina the respectable amongst them (the Ansar) would turn away the mean (the emigrants). Thereupon 'Umar said: Permit me so that I should strike the neck of this hypocrite. But he (the Holy Prophet) said: Leave him, the people may not say that Muhammad kills his companions. (Using translation from Muslim 2584b)
كَسَعَ رَجُلٌ مِنَ الْمُهَاجِرِينَ رَجُلًا مِنَ الْأَنْصَارِ فَقَالَ الْأَنْصَارِيُّ يَا لَلْأَنْصَارِ وَقَالَ الْمُهَاجِرِيُّ يَا لَلْمُهَاجِرِينَ قَالَ فَسَمِعَ النَّبِيُّ ﷺ ذَاكَ فَقَالَ «مَا بَالُ دَعْوَى الْجَاهِلِيَّةِ؟ » فَقَالُوا يَا رَسُولَ اللَّهِ رَجُلٌ مِنَ الْمُهَاجِرِينَ كَسَعَ رَجُلًا مِنَ الْأَنْصَارِ فَقَالَ «دَعُوهَا فَإِنَّهَا مُنْتِنَةٌ» فَقَالَ عَبْدُ اللَّهِ بْنُ أَبَيِّ ابْنُ سَلُولٍ قَدْ فَعَلُوهَا لَئِنْ رَجَعْنَا إِلَى الْمَدِينَةِ لَيُخْرِجَنَّ الْأَعَزُّ مِنْهَا الْأَذَلَّ فَقَالَ عُمَرُ دَعْنِي يَا رَسُولَ اللَّهِ أَضْرِبْ عُنُقَ هَذَا الْمُنَافِقِ فَقَالَ «دَعْهُ لَا يَتَحَدَّثُ النَّاسُ أَنَّ مُحَمَّدًا يَقْتُلُ أَصْحَابَهُ»