(34) بَاب صِيَامِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فِي غَيْرِ رَمَضَانَ وَاسْتِحْبَابِ أَنْ لَا يُخْلِيَ شَهْرًا عَنْ صَوْمٍ
Abdullah b. Shaqiq reported. I asked 'A'isha (Allah be pleased with her) about fasting of the Messenger of Allah (ﷺ). She said:
He used to observe fast (at times) so continuously that we said: He has fasted, he has fasted. And (at times) he did not observe fast (for days) and we began to say: He has abandoned fasting, he has abandoned fasting. She said: I did not see him observing fast throughout the whole of the month since he arrived in Medina, but that of Ramadan.
Reference: Sahih Muslim 1156 c
In-book reference: Book 13, Hadith 225
USC-MSA web (English) reference(deprecated numbering scheme): Book 6, Hadith 2578