(52) باب صَوْمِ شَعْبَانَ
Narrated `Aisha:
Allah's Messenger (ﷺ) used to fast till one would say that he would never stop fasting, and he would abandon fasting till one would say that he would never fast. I never saw Allah's Messenger (ﷺ) fasting for a whole month except the month of Ramadan, and did not see him fasting in any month more than in the month of Sha'ban.
Reference: Sahih al-Bukhari 1969
In-book reference: Book 30, Hadith 76
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 3, Book 31, Hadith 190