Sayyidah Aishah (may Allah be pleased with her) said that the Messenger of Allah (peace and blessings be upon him) did not fast any month of the year except Sha'ban; he used to fast the whole of Sha'ban.
Sayyidah Aishah (may Allah be pleased with her) said: I did not see him (peace and blessings be upon him) fasting more in any month than in Sha'ban. In one narration it states that he used to fast the whole of Sha'ban; it is also stated that he (peace and blessings be upon him) left only a few fasts of Sha'ban, rather he fasted the whole of Sha'ban.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 7964