It is narrated from Sayyidah Umm Salamah (may Allah be pleased with her) that the Prophet (peace and blessings be upon him) never fasted a complete month, except that he (peace and blessings be upon him) used to fast Sha'ban and join it to Ramadan.
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 19831
Sayyidah Aishah and Sayyidah Umm Salamah (may Allah be pleased with them both) both said: "The Prophet (peace and blessings be upon him) did not fast any month other than Ramadan except Sha'ban, for he (peace and blessings be upon him) used to join it to Ramadan, and so they would become two consecutive months. And he (peace and blessings be upon him) would sometimes fast so much that we would say he will not stop fasting, and sometimes refrain so much that we would say he will not fast."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 19832
It is narrated from Sayyidah Umm Salamah (may Allah be pleased with her) that the Prophet (peace and blessings be upon him) used to fast Sha'ban and Ramadan.
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 19833