عَنْ أَبِي ذَرٍّ رَضِيَ اللَّهُ عَنْهُ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ: ((مَنْ كَانَ صَائِمًا مِنَ الشَّهْرِ ثَلَاثَةَ أَيَّامٍ فَلْيَصُمِ الثَّلَاثَ الْبِيضَ))
It is narrated from Sayyiduna Abu Dharr (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: Whoever among you wishes to fast three days in a month, let him fast on the three days of Ayyam al-Beedh (the white days).