Sahih Al Bukhari – Book of Praying At Night In Ramadaan (Taraweeh)
Volumn 003, Book 032, Hadith Number 241.
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Narated By 'Aisha RA : With the start of the last ten days of Ramadan, the Prophet PNUH used to tighten his waist belt (i.e. work hard) and used to pray all the night, and used to keep his family awake for the prayers.