Sahih Bukhari, Chapter: Call to Prayers (Adhaan)

"When the Prophet became seriously ill and his disease became aggravated he asked for permission from his wives to be nursed in my house and he was allowed. He came out with the help of two men and his legs were dragging on the ground. He was between Al-Abbas and another man." 'Ubaid Ullah said, "I told Ibn 'Abbas what 'Aisha had narrated and he said, 'Do you know who was the (second) man whose name 'Aisha did not mention'" I said, 'No.' Ibn 'Abbas said, 'He was 'Ali Ibn Abi Talib.' "