صَحِيحُ مُسْلِمٍ
Sahih Muslim 1156 f
The Book of Fasting
The Prophet's Fasts at times other than Ramadan; and it is recommended to ensure that no month is free of fasting
وَحَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، وَعَمْرٌو النَّاقِدُ، جَمِيعًا عَنِ ابْنِ عُيَيْنَةَ، - قَالَ أَبُو بَكْرٍ حَدَّثَنَا سُفْيَانُ بْنُ عُيَيْنَةَ، - عَنِ ابْنِ أَبِي لَبِيدٍ، عَنْ أَبِي سَلَمَةَ، قَالَ سَأَلْتُ عَائِشَةَ - رضى الله عنها - عَنْ صِيَامِ رَسُولِ اللَّهِ صلى الله عليه وسلم فَقَالَتْ كَانَ يَصُومُ حَتَّى نَقُولَ قَدْ صَامَ . وَيُفْطِرُ حَتَّى نَقُولَ قَدْ أَفْطَرَ . وَلَمْ أَرَهُ صَائِمًا مِنْ شَهْرٍ قَطُّ أَكْثَرَ مِنْ صِيَامِهِ مِنْ شَعْبَانَ كَانَ يَصُومُ شَعْبَانَ كُلَّهُ كَانَ يَصُومُ شَعْبَانَ إِلاَّ قَلِيلاً .
Abu Salama reported: I asked 'A'isha (Allah be pleased with her) about the fasting of the Messenger of Allah (ﷺ). She said: He used to observe fast (at times so continuously) that we said: He has fasted (never to break), and he did not observe fast till we said: He has given up perhaps never to fast, and I never saw him observing (voluntary fasts) more in any other month than that of Sha'ban. (lt appeared as if) he observed fast throughout the whole of Sha'ban except a few (days).
Sahih Muslim, 1156 fSahihصحيح