The days of Ramadan are over for this year, but that does not mean that the days of accruing great rewards are as well.
The Messenger of Allah (ﷺ) said,
“Whoever fasts Ramadan and then follows it with six days of Shawwal, it is as if he fasted for a lifetime.”  
Scholarly views on how to perform these fasts
They fell into three main groups.
However, the majority consider it to be a highly recommended act. 
The first group, which included Imam al-Shāfi’ī and Ibn al-Mubārak, considered it to be highly recommended to fast consecutively from the beginning of the month.
The second group opined that there was no problem in fasting successively or separately.
This was the view of Imam Ahmad.
The last group (Ma’mar and Abdul-Razzāq) suggested that these days should not be performed straight after Eid al-Fitr, as this is the time of eating and drinking.
Rather, it is better that these six days coincide with Ayyām al-Bīd (the 13th, 14th, and 15th of each month), the remaining three days can be performed on either side of these days.
The virtues of fasting
The fasting of Shawwal is like fasting in Sha’bān; both of these months are wedded to Ramadan.
Whilst the fasting in Sha’bān serves to prepare the believer for Ramadan, Shawwal is like demonstrating gratitude to Allah for bestowing us with Ramadan.
The one who fasts the six days of Shawwal after completing the fasts of Ramadan is like one who has fasted continuously, as a good deed is multiplied by ten (i.e. 36 days of fasts is equivalent to 360 days – a full lunar year).
The Prophet (ﷺ) said,
“Fasting Ramadan is like fasting ten months, and fasting six days is like fasting two months. That is like fasting a whole year.” 
This is irrespective of whether Ramadan is 29 or 30 days, because of the saying of the Prophet (ﷺ),
“The two months of Eid, Ramadan, and Dhu’l-Hijjah will never be lessened.” 
The meaning of this is that these two months will not be lessened in terms of their rulings.
It could be argued that that these six days can be performed during any time of the year to gain the bounty. However, the virtue is connected to fasting in Shawwal, specifically because it is attached to Ramadan.
This exclusivity for Shawwal has been mentioned by some scholars like ‘Abdullāh ibn al-Mubārak as reported in al-Tirmidhi. 
Benefits of fasting straight after Ramadan
Firstly, fasting the six days of Shawwal after completing the days of Ramadan is like fasting for the entire year.
Secondly, fasting in Sha’bān and Shawwal is like praying the voluntary prayers that come before and after an obligatory prayer.
Similar to those prayers, the Sha’bān fasts prepare the believer for Ramadan, whilst the Shawwal ones compensate for any deficiencies in the obligatory Ramadan fasts.
For this reason, ‘Umar ibn ‘Abd al-‘Azīz is reported as saying,
“Whoever finds nothing to give charity with, let him fast.”
Just as one of the wisdoms of Zakat al-Fitr is to make up for any defects in the Ramadan fasts, ‘Umar ibn ‘Abd al-‘Azīz suggests that if a person cannot afford this, then he should fast in its place, as is done for other legislated acts such as violated oaths, and so on.
Thirdly, it is a sign that the fasts of Ramadan have been accepted.
If Allah accepts an act of worship, surely He will give the believer an opportunity to perform an act similar to it.
One of the scholars said,
“The reward for a good deed is the good deed that follows it. So, whoever does a good deed and then follows it up with another one, that (the second good deed) is a sign of acceptance for the first good one.”
Fourthly, the fasting of these six days represents thankfulness to Allah for giving us Ramadan.
One of the Muslims in the early generations would fast as an act of thankfulness to Allah when he was given the opportunity to spend the night in prayer.
Likewise, Wuhayb ibn al-Ward was asked about the reward for actions such as Tawwāf or something like it.
“Do not ask about its reward. Rather, ask about what form of thankfulness is incumbent upon one who was blessed to undertake the act.”
This is at odds with the one who planned to return back to sin whilst fasting in Ramadan, for this is a sign of a rejected Ramadan.
Fifthly, this helps the slave to continue to do the acts that he started in Ramadan.
The Messenger of Allah (ﷺ) said,
“The best deed in the sight of Allah is that which is done regularly.” 
Do not let the fasting of Ramadan be like how many of us recite the Qur’ān – we begin reciting it in Ramadan and end it there, not returning to it for another year!
Rather, our endeavours should be continuous, such that the recitation of Surat al-Nas is followed by al-Fatiha and al-Baqarah. Every time we complete the Qur’ān, we begin it again.
Make up for what you missed in Ramadan
The Prophet (ﷺ) would use Shawwal to make up for any actions that he missed in Ramadan.
For instance, he didn’t perform the ‘itikāf during the last 10 days one year, so he made it up in the beginning of Shawwal.
There is a difference of opinion amongst the scholars  as to whether the fasts that need to be made up from Ramadan must be performed before fasting the six days of Shawwal, in order to reap the reward for fasting the entire year.
The alternative is to fast the six days and make up the missed fasts later, even if it was just before the next Ramadan. This seemed to have been done by ‘Ā’ishah (radiy Allāhu ‘anhā).
It is better to be on the safe side and make up the missed fasts of Ramadan before the fasts of Shawwal.
Obedience tied with time
The different times of the months within a year are connected to varying acts of obedience.
Each month is tied to a target or a milestone of acts of obedience, some periods more than others. These targets took on such an important form that the scholars divided the Qur’ān into thirty sections in order to correspond to the thirty days of the month – for it to be a measure of our own actions.
The chance to perform such actions do not expire until the date of our death.
al-Hasan al-Basri stated,
“Allah has fixed no expiration date for a believer’s devotional action, other than death.”
He then recited the words of Allah,
“Worship your Lord until death comes to you.” 
 This article is predominantly based on Ibn Rajab’s Latā’if al-Ma’ārif, with the ahādīth being checked by Amir ibn Ali Yasin.
 Ibn Rajab stated that it was the position of Imam Abū Hanīfah, Abū Yūsuf, and Sufyān al-Thawrī that it was disliked to fast these six days. However, the later Hanafis considered it to be recommended.
Imam Mālik did not know any of the people of Madinah to perform this practice; he therefore feared it was close to being an innovation. Ibn Rushd stated that perhaps the hadīth did not reach Imam Mālik. (Bidāyat al-Mujtahid).
The scholars who opined its desirability were Ibn ‘Abbās, Ibn al-Mubarak, Ahmad, and others.
 Ahmad & Ibn Mājah
 Bukhāri & Muslim
 It is quite possible that he depended on a narration of Umm Salama (which happens to be weak) in which she mentioned,
“Whoever fasts the day after Eid al-Fitr, it is as if they have fasted from Ramadan.”
 The Hanafis and Mālikis mention that the qadha fasts of Ramadan do need to be made up before the six fasting days of Shawwal can be performed as the time of qadha is wide.
Many of the Shāfi’īs and Hanbalis state that the qadha must be made up before the six days can be fasted.
 al-Qur’ān, 16:99
This article was originally published on 14 August 2013/ 07 Shawwal 1434, before an initial revision on 26 June 2017/ 02 Shawwal 1438, and a further republication on 22 April 2023/ 02 Shawwal 1444.