Muwatta Malik, Book 18, Hadith 689 (In-Book) ⓘ

Yahya related to me from Malik from Abu'n Nadr, the mawla of Umar ibn Ubaydullah, from Abu Salama ibn Abd ar-Rahman that A'isha, the wife of the Prophet, may Allah bless him and grant him peace, said, "The Messenger of Allah, may Allah bless him and grant him peace, used to fast for so long that we thought he would never stop fasting, and he would go without fasting for so long that we thought he would never fast again. I never saw the Messenger of Allah, may Allah bless him and grant him peace, fast for a complete month except for Ramadan, and I never saw him do more fasting in any one month than he did in Shaban.'

حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنْ أَبِي النَّضْرِ، مَوْلَى عُمَرَ بْنِ عُبَيْدِ اللَّهِ عَنْ أَبِي سَلَمَةَ بْنِ عَبْدِ الرَّحْمَنِ، عَنْ عَائِشَةَ، زَوْجِ النَّبِيِّ صلى الله عليه وسلم أَنَّهَا قَالَتْ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم يَصُومُ حَتَّى نَقُولَ لاَ يُفْطِرُ وَيُفْطِرُ حَتَّى نَقُولَ لاَ يَصُومُ وَمَا رَأَيْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم اسْتَكْمَلَ صِيَامَ شَهْرٍ قَطُّ إِلاَّ رَمَضَانَ وَمَا رَأَيْتُهُ فِي شَهْرٍ أَكْثَرَ صِيَامًا مِنْهُ فِي شَعْبَانَ ‏.‏