Sha'ban fasting
AnnualAisha reported that the Prophet ﷺ fasted more in Sha'ban than in any other month outside of Ramadan. Sha'ban is the month before Ramadan.
Hadith
لَمْ يَكُنِ النَّبِيُّ صلى الله عليه وسلم يَصُومُ شَهْرًا أَكْثَرَ مِنْ شَعْبَانَ فَإِنَّهُ كَانَ يَصُومُ شَعْبَانَ كُلَّهُ
"The Prophet ﷺ never fasted in any month more than in the month of Sha'ban. He used to fast all of Sha'ban."
Reward
The Prophet ﷺ fasted in Sha'ban more than any other month outside of Ramadan.