narrated 'aisha (radi-allahu 'anha): whenever allah's apostle (sallallahu 'alaihi wa sallam) became sick, he would recite mu'awwidhat (surat al-falaq and surat an-nas) and then blow his breath over his body. when he became seriously ill, i used to recite (these two suras) and rub his hands over his body hoping for its blessings. bukhari vol. 6 : no. 535