Mukhtasar Muslim (Abridged) 618 — Fasting six days of Shawwal after

It is narrated from Sayyiduna Abu Ayyub Ansari (may Allah be pleased with him) that the Messenger of Allah (peace and blessings of Allah be upon him) said: Whoever fasts in Ramadan and then follows it with six days of fasting in Shawwal, it is as if he has fasted for the whole year.