Musnad Ahmad 1153:874

'Affan narrated to us, he said: Hammad narrated to us, from Hammad, from Ibrahim, from al-Aswad, from 'Aisha, she 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 for the Highest, Most Blessed Companion."