Narrator:Abu Dharr
وعن أبي ذر رضي الله عنه، قال: قال رسول الله صلى الله عليه وسلم:
"إذا صمت من الشهر ثلاثًا، فصم ثلاث عشرة، وأربع عشرة وخمس عشرة"
Abu Dharr (may Allah be pleased with him) reported that the Messenger of Allah (may Allah’s peace and blessings be upon him) said: "If you fast three days of the month, then fast the thirteenth, fourteenth and fifteenth."
Qatādah ibn Milhān (may Allah be pleased with him) reported that the Messenger of Allah (may Allah’s peace and blessings be upon him) used to order us to fast the White Days: the thirteenth, fourteenth and fifteenth (of every lunar month)."
Ibn ‘Abbās (may Allah be pleased with him) reported that the Messenger of Allah (may Allah’s peace and blessings be upon him) never broke his fast on the White Days, whether he was a resident or a traveler.”
Reported by At-Tirmidhi (No. 761) and An-Nasa’i (No. 2422, 2423, 2424). Cited in Riyad as-Salihin (No. 1262).