It wasnarrated from 'Abdul-Malik bin Minhal, from his father that:
TheMessenger of Allah (ﷺ) used to enjoin fasting the bright days –the thirteenth, fourteenth and fifteenth (when the moon is full). Hesaid: "It is like fasting for a lifetime." (FR)
English reference (FR): Vol. 1, Book 7, Hadith 1707 (FR)
Arabic reference (FR): Book 7, Hadith 1777 (FR)