Narrated 'Aishah, wife of Prophet (ﷺ):The Messenger of Allah (ﷺ) used to fast to such an extent that we thought that he would never break his fast, and he would go without fasting to such an extent that we thought he would never fast. I never saw the Messenger of Allah (ﷺ) fast a complete month except in Ramadan, and I never saw his fast more in any month than in Sha'ban

English translation · Sunan Abu Dawud