Musnad Ahmad Hadith 24253

It is narrated from Aisha (may Allah be pleased with her) that once during his final illness, the Prophet (ﷺ) said, "Call some of my companions to me." I said, "Abu Bakr?" The Prophet (ﷺ) said, "No." I said, "Umar?" He said, "No." I said, "Umar?" He said, "No." I said, "Shall I call Uthman?" The Prophet (ﷺ) said, "Yes!" When he came, the Prophet (ﷺ) told me to move away from there and began to speak to him in whispers. During this, the color of Uthman's (may Allah be pleased with him) face kept changing. Then, when Uthman (may Allah be pleased with him) was besieged on the day of the house, we said to him, "O Leader of the Believers! Why do you not fight?" He replied, "No, the Prophet (ﷺ) took a covenant from me, and I will remain steadfast upon it."