It was narrated that Abu Salamah said:“I asked ‘Aishah about the fasting of the Prophet (ﷺ). She said: ‘He used to fast until we thought he would always fast. And he used to not fast until we thought he would always not fast. I never saw him fast more in any month than in Sha’ban. He used to fast all of Sha’ban; he used to fast all of Sha’ban except a little.’”

English translation · Sunan Ibn Majah