Fasting in Shawwal & Muharram
[Sahih Muslim : Book 6 Kitab Al-Sawm, Number 2614]
Abu Ayyub al-Ansari (Radi Allah Anhu) reported Allah's Messenger (sal-allahu-alleihi-wasallam) as saying: He who observed the fast of Ramadan and then followed it with six (fasts) of Shawwal. it would be as if he fasted perpetually.