Riyad as-Salihin
Riyad as-Salihin 1260
The Desirability of Observing Three Days of Fasting in Every Month
Arabic hadith text
وعن عبد الله بن عمرو بن العاص، رضي الله عنهما، قال: قال رسول الله: "صوم ثلاثة أيام من كل شهر صوم الدهر كله" ((متفق عليه))
Translation
'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].