First Ayesha...
First Ayesha, Talha and Zubayr, and then Muawiya and Amr bin Aas rose as his (Uthman's) protagonists to seek vengeance for his blood. Whatever the various and often murky impulses of those men and women who rallied round the corpse of Uthman, it is clear that his safety was not the least of their concerns. This is a fact that cannot be controverted but it's also a fact that Sunni historians do not wish to rake up.
It is much more comforting and easier for them to allege that Muhammad ibn Abu Bakr or Malik ibn Ashter were involved in the assassination of Uthman than to admit that Ayesha, Talha, Zubayr, Muawiya and Amr bin Aas, all played a role in the grisly tragedy of the old khalifa's death. Malik ibn Ashter died at a time when Ali needed him most, and there was no one who could take his place.
The shock to Ali, of the death of friends like Ammar ibn Yasir and Malik ibn Ashter, was devastating but he was sustained by his Faith. He considered each new shock, each new sorrow, and each new misfortune, a new test of his faith, and it remained unshaken. His faith in the mercy of his Creator was greater than anything that could ever befall him, and he never surrendered to despair. Malik was truly extraordinary.
He was the consummate military professional, dedicated, dignified, and supremely competent and self-confident. He was a king among men. A more remarkable man than him in his bold and salient individuality, and sharply marked light and shadow, is nowhere to be seen in Arabian history. Propaganda has made the names of some other men more well-known than his but he remains incomparable. He was the Phoenix of Islam.
Perhaps it is impossible to pay Malik ibn Ashter a tribute greater than the one paid to him by his own master, Ali ibn Abi Talib. In the battle of Layla-tul-Harir, Ali placed his hands on the shoulders of Malik, and said: “You have served me with the same distinction and devotion with which I served my master, Muhammad, the blessed Apostle of God.” The Loss of Egypt Amr bin Aas entered Egypt without any opposition, and when he encountered Muhammad ibn Abu Bakr, he easily defeated him.
Muhammad had no army, and he tried to fight with a handful of soldiers. The Syrians captured him, and tortured him to death. Amr occupied Egypt, and it became a part of Muawiya's dominions. Ali loved Muhammad ibn Abu Bakr as his own son. His death was another terrible shock he had to endure.