Hadith 1792
It is narrated from Sayyiduna Abu Ayyub Ansari (may Allah be pleased with him) that the Messenger of Allah (peace and blessings 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."
Hadith 1793
It is narrated from Sayyiduna Thawban (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: “(The fasting of a year is like this:) the fasting of one month is equal to ten months, and after that, the fasting of six days is equal to two months, thus making twelve months and completing a whole year.” That is, one month of Ramadan and after it, six fasts of Shawwal.