Musnad Ahmad 1153:1465

'Abd al-Rahman narrated to us, from Malik, from al-Zuhri, from 'Urwah, from 'Aishah, from the Prophet, peace and blessings of Allah be upon him, that he used to: "When he was ill, he would recite over himself the Mu'awwidhat (the chapters of seeking refuge), and he would blow (with a light spittle)."