Fasting (Kitab Al-Siyam)

Dawud :: Book 13 : Hadith 2443

Narrated Qatadah Ibn Malhan al-Qaysi:

The Apostle of Allah (peace_be_upon_him) used to command us to fast the days of the white (nights): thirteenth, fourteenth and fifteenth of the month. He said: This is like keeping perpetual fast.