Hadith: O Khālid, after me, events, trials, and divergence will occur. So if you can be the servant of Allah who is killed, and not the one killing, then do so

عن خالد بن عُرْفُطَةَ رضي الله عنه قال: قال لي رسول الله صلى الله عليه وسلم : "يا خالد إنها ستكون بَعْدِي أَحْدَاثٌ وفِتَنٌ واختلاف، فَإِنِ اسْتَطَعْتَ أن تكون عبد الله المقتول لا القاتل فَافْعَلْ".
[صحيح] - [رواه أحمد]

Khālid ibn ‘Urfutah (may Allah be pleased with him) reported: The Messenger of Allah (may Allah's peace and blessings be upon him) said to me: "O Khālid, after me, events, trials, and divergence will occur. So if you can be the servant of Allah who is killed, and not the one killing, then do so."
[Authentic hadith] - [Narrated by Ahmad]

Explanation

The Prophet (may Allah's peace and blessings be upon him) told Khālid ibn ‘Urfutah that there will be differences, wars, and trials in the future. For example, the Muslim Ummah will not have a ruler at all, or there will be a leader for each territory. Therefore, dissensions and wars will arise among them. The Prophet (may Allah's peace and blessings be upon him) ordered Khālid to isolate himself from such temptations and not engage in them; to be killed unjustly would be better for him than to kill a Muslim. In this case, it is recommended to confine oneself to one's house or to completely move from the affected country. However, there is a proof that one may defend oneself, one's family, and one's property at times of tribulation. He is to be excused for killing or being killed, unless corruption and conflicts arise from that. If the Muslims are united around an Imām, regardless of whether he is just or despotic, and a group of people rebel against him, and they have some power and want to create dissension, then the Imām should communicate with them. If they refuse to obey him and scared the Muslims, then the Imām should fight them so as to restrain their evil. The people should side with the Imām in fighting those rebels until they come back in conciliation, return to Allah's commands, and obey the leadership. This applies to oppressors as well as those who rebel against the ruler and leave his obedience.