Once, Hazrat Umar (may Allah be pleased with him) asked, "Who among you was present on the occasion of 'Yawm al-Qahah'?" Hazrat Abu Dharr (may Allah be pleased with him) replied, "I was present, and the Noble Prophet (peace and blessings be upon him) instructed that man to fast on the white days, that is, the 13th, 14th, and 15th of the month."