Sahih Al Bukhari – Book of Invocations

Volumn 008, Book 075, Hadith Number 331.
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Narated By 'Aisha : Whenever Allah's Apostle went to bed, he used to blow on his hands while reciting the Mu'auwidhat (i.e. Suratal-Falaq and Surat-an-Nas, 113 and 114) and then pass his hands over his body.