Sahih Muslim Book 4, Hadith 100
When the Messenger of Allah (ﷺ) fell ill and his illness became serious, he asked permission from his wives to stay in my house during his illness. They gave him permission to do so. He stepped out (of'A'isha's apartment for prayer) supported by two persons. (He was so much weak) that his feet dragged on the ground and he was being supported by 'Abbas b. 'Abd al-Muttalib and another person. 'Ubaidullah said: I informed 'Abdullah (b. 'Abbas) about that which 'A'isha had said. 'Abdullah b. 'Abbas said: Do you know the man whose name 'A'isha did not mention? He said: No. Ibn 'Abbas said: It was 'Ali.
It was in the house ofMaimuna that the Messenger of Allah (ﷺ) first fell ill. He asked permission from his wives to stay in her ('A'isha's) house during his illness. They granted him permission. She ('A'isha) narrated: He (the Holy Prophet) went out (for prayer) with his hand over al-Fadl b. 'Abbas and on the other hand there was another person and (due to weakness) his feet dragged on the earth. 'Ubaidullah said: I narrated this hadith to the son of 'Abbas ('Abdullah b. 'Abbas) and he said: Do you know who the man was whose name 'A'isha did not mention? It was 'Ali.
I tried to dissuade the Messenger of Allah (ﷺ) from it (i. e. from appointing Abu Bakr as the Imam.) and my insistence upon it was not due to the fact that I entertained any apprehension in my mind that the people would not love the man who would occupy his (Prophet's) place (i. e. who would be appointed as his caliph) and I feared that the people would be superstitious about one who would occupy his place. I, therefore, desired that the Messenger of Allah (ﷺ) should leave Abu Bakr aside in this matter.