Sahih Bukhari
Sahih Bukhari Volume 001, Book 012, Hadith Number 718.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 12. Charecteristics Of Prayer
Narated By 'Aisha : I asked Allah's Apostle about looking hither and thither in prayer. He replied, "It is a way of stealing by which Satan takes away (a portion) from the prayer of a person."