رِيَاضُ الصَّالِحِينَ
Riyad as-Salihin 1258
The Book of Virtues
The Desirability of Observing Three Days of Fasting in Every Month
وَعَنْ أَبِي هُرَيْرَةَ رَضِيَ اللَّهُ عَنْهُ قَالَ: أَوْصَانِي خَلِيلِي صَلَّى اللَّه عَلَيْهِ وَسَلَّمَ بِثَلاَثٍ: صِيَامِ ثَلاَثَةِ أَيَّامٍ مِنْ كُلِّ شَهْرٍ، وركعتي الضُّحَى وَأَنْ أُوتِرَ قَبْلَ أَنْ أَنَامَ. ((مُتَّفَقٌ عَلَيْهِ))
Abu Hurairah (May Allah be pleased with him) reported: My friend (the Messenger of Allah) (ﷺ) directed me to observe fast for three days in every month, to perform two Rak'ah (optional) Duha prayer at forenoon and to perform the Witr prayer before going to bed. [Al-Bukhari and Muslim].
Riyad as-Salihin, 1258