Mukhtasar Bukhari

Umm al-Mu’minin Aisha Siddiqa (may Allah be pleased with her) says that when the Prophet Muhammad (peace and blessings be upon him) used to observe voluntary fasts, he would fast so much that we would think he would never stop fasting, and when he would stop, he would stop so much that we would think he would never fast again. And I did not see the Messenger of Allah (peace and blessings be upon him) observe a full month of fasting except in Ramadan, and I did not see him fast in any month more than in Sha’ban.