A'isha (RAA) narrated, "The Messenger of Allah (ﷺ) used to fast until one would say, he never breaks his fast (i.e. he never stops fasting), and he would abandon fasting (at other times) until one would say that he never fasts. And I never saw the Messenger of Allah (ﷺ) fast for a complete month except for the month of Ramadan, and I never saw him fast in a month more than he did in the month of Sha'ban." Agreed upon and the wording is from Muslim.