Musnad Ahmad 1153:918

'Affan narrated to us, Hammad narrated to us, from Hammad, from Ibrahim, from al-Aswad, from 'Aishah, who said: When the Prophet, peace and blessings of Allah be upon him, became ill, I took his hand and began to wipe it over his chest, and I supplicated with these words: "Remove the affliction, O Lord of the people." He pulled his hand away from my hand and said: "I ask Allah, the Mighty and Majestic, for the Highest Companion, the Most Blessed."