رِيَاضُ الصَّالِحِينَ
Riyad as-Salihin 1260
The Book of Virtues
The Desirability of Observing Three Days of Fasting in Every Month
وَعَنْ عَبْدِ اللَّهِ بْنِ عَمْرِو بْنِ الْعَاصِ، رَضِيَ اللَّه عَنْهُمَا، قَالَ: قَالَ رَسُولُ اللَّهِ: صَوْمُ ثَلَاثَةِ أَيَّامٍ مِنْ كُلِّ شَهْرٍ صَوْمُ الدَّهْرِ كُلِّهِ ((مُتَّفَقٌ عَلَيْهِ))
'Abdullah bin 'Amr bin Al-'As (May Allah be pleased with them) reported: The Messenger of Allah (ﷺ) said, "Observing Saum (fasting) on three days of every month is equivalent to a full month's fasting." [Al-Bukhari and Muslim].
Riyad as-Salihin, 1260