´It was narrated that Musa bin Talhah said:` "I heard Abu Dharr, at Ar-Rabadhah, saying: 'The Messenger of Allah said: if you want to fast at any time during the monthm then fast on the thirteenth, fourteenth and fifteenth."'
Hadith ReferenceSunan an-Nasa'i / The Book of Fasting / Hadith: 2426