Volume 3, Book 31, Number 202:
Narrated Abu Huraira:
My friend (the Prophet ) advised me to observe three things:
(1) to fast three days a month;
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SAHIH BUKHARI VOLUME 3 > BOOK 31: FASTING
(2) to pray two Rakat of Duha prayer (fore-noon prayer); and
(3) to pray Witr before sleeping.