Ayyub (Allah be pleased with him) relates that the Messenger of Allah (blessings and peace be upon him, his family, and companions) said, “Whoever fasts Ramadan and follows it with six days from Shawwal it is as if they fasted the entire year.”
[Muslim, Abu Dawud, Tirmidhi, and Ibn Majah; Ahmad transmitted it from Jabir, Muntaqa]
Thawban (Allah be pleased with him) relates that the Messenger of Allah (blessings and peace be upon him, his family, and companions) said, “Whoever fasts Ramadan, and then six days after Eid, it is [like fasting] an entire year. Whoever does a good deed shall have ten times its reward.”
[Ibn Majah, Muntaqa]
Now It is permitted to fast these six days separately throughout the month, or consecutively, after Eid al-Fitr.
But it is better to keep them as soon as the month starts “In order to hasten to do the good, and because of the problems inevitable in delaying,” such as becoming lazy and not actually fulfilling this sunna in the end, Abu Hurayra (Allah be pleased with him) said that
the Prophet (Allah bless him & give him peace) said,
“The strong believer is better and more beloved to Allah than the weak believer, though there is good in both. Be avid for that which benefits you. Rely on Allah and do not deem yourself incapable…”
[Muslim 4816, Ibn Majah 76, Ahmad 8436]
Imam Nawawi (Allah have mercy on him) explained that the ‘strength’ in this hadith refers to, “One’s determination and ability in matters of the next life.”
[Sharh Sahih Muslim]
