'Aishah (May Allah be pleased with her) reported:
The Prophet (ﷺ) did not observe voluntary Saum (fasting) so frequently during any other month as he did during Sha'ban. He observed Saum throughout the month of Sha'ban.Another narration is: He (ﷺ) observed Saum during the whole month of Sha'ban except a few days.[Al- Bukhari and Muslim].
App reference: Book 9, Hadith 257
Arabic/English book reference: Book 9, Hadith 1247