Musnad Abu Ya'la al-Mawsili 150:356

Al-Abbas ibn al-Walid al-Narsi narrated to us, Sufyan ibn Uyaynah narrated to us, from Ibn Abi Labid, who heard Abu Salamah say: I came to Aisha and said, "O Mother, inform me about the prayer of the Messenger of Allah (may Allah bless him and grant him peace)." She said, "His prayer at night, in the month of Ramadan and other than it, was thirteen rak'ahs, including the two rak'ahs of Fajr." I said, "Inform me about his fasting." She said, "He used to fast until we would say, 'He has fasted,' and he would break his fast until we would say, 'He has broken his fast.' And I never saw him fast a month in its entirety more than his fasting in Sha'ban; he used to fast all of Sha'ban, he used to fast Sha'ban except for a little."