Al-Matalib al-'Aliyah 4382 — The killing of Uthman bin Affan

It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that he said: "I was besieged (in the days of fitnah) with Sayyiduna Uthman bin Affan (may Allah be pleased with him) in his house. Meanwhile, the rebels shot an arrow at one of our companions and martyred him. So I submitted: O Commander of the Believers! Now the time for fighting has come (that is, it is now permissible to fight them); they have killed one of our men. At this Sayyiduna Uthman (may Allah be pleased with him) said: 'O Abu Hurayrah! I emphatically order you to throw down your sword, for their real aim is only to take my life, and I will protect the blood of the Muslims by offering my own self.' Sayyiduna Abu Hurayrah (may Allah be pleased with him) says: So I threw down my sword (at his order), and to this day I do not know where it went."
In the chain of this hadith, Khalid bin al-Qasim and Abu Ma'shar Najih bin Abd al-Rahman al-Madani are da'if (weak); however, Sayyiduna Uthman's (may Allah be pleased with him) forbidding the Companions from fighting in his defence is established by other reliable and authentic evidence.