Ash-Shama'il Al-Muhammadiyah, Book 42, Hadith 281 (English) ⓘ

'Abdullah bin Shaqeeq Radhiyallahu 'Anhu reports: "I inquired from 'Aayeshah Radhiyallahu 'Anha regarding the (nafil) saum of Rasulullah Sallallahu 'Alayhi Wasallam. She replied: 'At times Rasulullah Sallallahu 'Alayhi Wasallam fasted continuously. We used to say, he will keep on fasting (this month). At times he did not fast, till we began thinking he will not fast (that month). Rasulullah Sallallahu 'Alayhi Wasallam did not fast for a month after he came to Madinah, besides the fasts of Ramadhaan'".

حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، قَالَ‏:‏ حَدَّثَنَا حَمَّادُ بْنُ زَيْدٍ، عَنْ أَيُّوبَ، عَنْ عَبْدِ اللهِ بْنِ شَقِيقٍ، قَالَ‏:‏ سَأَلْتُ عَائِشَةَ، عَنْ صِيَامِ رَسُولِ اللهِ صلى الله عليه وسلم، قَالَتْ‏:‏ كَانَ يَصُومُ حَتَّى نَقُولَ قَدْ صَامَ، وَيُفْطِرُ حَتَّى نَقُولَ قَدْ أَفْطَرَ قَالَتْ‏:‏ وَمَا صَامَ رَسُولُ اللهِ صلى الله عليه وسلم، شَهْرًا كَامِلا مُنْذُ قَدِمَ الْمَدِينَةَ إِلا رَمَضَانَ‏.‏