Lady Aisha Siddiqa (may Allah be pleased with her) narrates: The Prophet Muhammad (peace be upon him) used to observe (voluntary) fasts to such an extent that we would think he would never stop fasting, and sometimes he would stop observing voluntary fasts to such an extent that we would think he would not fast at all. I never saw the Prophet Muhammad (peace be upon him) fasting in any month more than he did in Sha'ban, except for Ramadan.