Narrated by Sayyida Aisha (may Allah be pleased with her), the wife of the Prophet ﷺ: The Messenger of Allah ﷺ used to fast (continuously) to the extent that we would say he will not break his fast, and when he would break his fast, we would say he will not fast anymore. I did not see him fast an entire month except for Ramadan, and I did not see him fast more in any month than in Ramadan.
Hadith Referenceالسنن المأثورة / باب صيام من أصبح جنبا / 315
Hadith Takhrijصحيح بخاري، الصوم، باب صوم شعبان، رقم : 2434، صحيح مسلم ،الصيام، باب صيام النبى فى غير رمضان، رقم : 1156