Sahih Bukhari Volume 5, Book 59, Hadith Number 723.

Narrated By ‘Aisha : Whenever Allah’s Apostle became ill, he used to recite the Muawidhatan and blow his breath over himself (after their recitation) and rubbed his hands over his body. So when he was afflicted with his fatal illness. I started reciting the Muawidhatan and blowing my breath over him as he used to blow and made the hand of the Prophet pass over his body.