My beloved friend instructed me to do three things, to fast three days of every month, to pray the two units of Duha, and to perform the Witr prayer before going to sleep.
أوصاني خليلي بثلاث: صيام ثلاثة أيام من كل شهر، وركعتي الضحى، وأن أوتر قبل أن أنام.
Bukhari narrated it in the Book of Fasting (1981), and Muslim in the Book of the Prayer of Travelers (721:85), through the route of Abdul-Warith, who said, "Abu Tayah narrated to us, Abu Uthman Nahdi narrated to me, from Abu Hurairah." This version states it without qualification as three days from every month, though it has also come qualified as the White Days. Bukhari is among those who hold that this should be understood as qualified, since he titled the chapter, "Chapter on fasting the White Days, the thirteenth, fourteenth, and fifteenth."