عَنْ أَبِي ذَرٍّ رَضِيَ اللَّهُ عَنْهُ عَنِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ قَالَ: ((مَنْ صَامَ ثَلَاثَةَ أَيَّامٍ مِنْ كُلِّ شَهْرٍ فَقَدْ صَامَ الدَّهْرَ كُلَّهُ))
Narrated by Sayyiduna Abu Dharr (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: Whoever fasts three days in every month, it is as if he has fasted for the whole year.