Fasting six days of the month of Shawwal is mentioned in a Prophetic hadith. The Prophet (peace and blessings be upon him) is reported to have said: "Whosoever fasted in Ramadan and then followed up with six fasting days of Shawwal, it is like fasting every day." (Muslim)

One of the ways to manifest our loving of Allah, by following the Prophet (salAllahu alayhi wasalam) is to do those acts that he (salAllahu alayhi wasalam) advised his Companions, and the Ummah in general, to do. A sunnah which is certainly relevant to us in these days is his(salAllahu alayhi wasalam) practice to fast six days in the month of Shawwal.

Abu Ayyub al-Ansari narrated that Allah’s Messenger (salAllahu alayhi wasalam) said: "He who fasts Ramadan, and six of Shawwal, it will be (in terms of rewards) as if the fasted a whole year." [Muslim, at-Tirmidhi, Abu Dawud, Ahmad, Ibn Majah]

So this is an established sunnah, which carries a great reward.

In commenting on the above mentioned hadith, As-San''ani said in Subul us-Salam: "If the thirty days of Ramadan fasting are assimilated with the six days of fasting in Shawwal, it altogether makes 36 days. According to Shari`ah, each virtue is rewarded ten times. Therefore, if we multiply 36 with 10, it makes 360, a number which equals the days of a year. Some scholars are of the opinion that these six days of fasting in Shawwal must be completed in a continuous order right after the end of Ramadan. Others believe that is enough to merely complete six days of fasting in Shawwal (in any order, either successive or with intervals), an opinion which is deemed to be correct." We may also fast on Mondays and Thursdays, as in that case we would be following another Sunnah: A’isha (radiAllahu anha) narrated: "The Messenger of Allah (salAllahu alayhi wasalam) used to fast Mondays and Thursdays". [an-Nasa''i]

If it is easier for one to fast on weekends, then in that case one would still be following another sunnah at the same time: Umm Salama (radiAllahu anha)narrated that Allah’s Messenger used to fast mostly on Saturday and Sunday, and he used to say: "They are the festival days for the mushrikeen, and I like to act contrary to them." [an-Nasa’i, Ibn Khuzaymah, who graded it saheeh, and Ibn Hajar agreed]

It was proven from Abu Ayyub (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Whosoever observes fast in Ramadan and then follows up with six fasts in Shawwal, will be regarded as though he had been fasting every day." (Reported by Ahmad, Muslim, Abu Dawud and At-Tirmidhi)

This is an authentic hadith, which indicates that fasting six days of Shawwal is a Prophetic sunnah. Imam Ash-Shafi`i, Ahmad, and a number of leading scholars and jurists followed this.

It is not correct to oppose this hadith with the reasons that some scholars cite for this fast being makruh, such as the fear that an ignorant person might think that this is part of Ramadan, or the fear that people may think this is obligatory, or that he did not hear that one of the earlier scholars used to fast these days, because this is all speculation, which cannot be used to oppose the authentic hadith mentioned above. If something is known, this is evidence against those who do not know.

The virtue of fasting six days of Shawwaal

Fasting six days of Shawwaal after the obligatory fast of Ramadaan is Sunnah Mustahabbah, not waajib. It is recommended for the Muslim to fast six days of Shawwaal, and in this there is great virtue and an immense reward. Whoever fasts these six days will have recorded for him a reward as if he had fasted a whole year, as was reported in a saheeh hadeeth from the Prophet (peace and blessings of Allaah be upon him). Abu Ayyoob (may Allaah be pleased with him) reported that the Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Whoever fasts Ramadaan and follows it with six days of Shawwaal, it will be as if he fasted for a lifetime.” (Narrated by Muslim, Abu Dawood, al-Tirmidhi, al-Nisaa’i and Ibn Maajah).

The Prophet (peace and blessings of Allaah be upon him) explained this when he said: “Whoever fasts for six days after (Eid) al-Fitr has completed the year: (whoever does a good deed (hasanah) will have ten hasanah like it).” According to another report: “Allaah has made for each hasanah ten like it, so a month is like fasting ten months, and fasting six days completes the year.” (al-Nisaa’i and Ibn Maajah. See also Saheeh al-Targheeb wa’l-Tarheeb, 1/421). It was also narrated by Ibn Khuzaymah with the wording: “Fasting for the month of Ramadaan brings the reward of ten like it, and fasting for six days brings the reward of two months, and that is the fasting of the whole year.”

The Hanbali and Shaafa’i fuqaha’ explained that fasting six days of Shawwaal after fasting Ramadaan makes it as if one has fasted for an entire year of obligatory fasts, because the multiplication of the reward applies even to naafil fasts, because each hasanah brings the reward of ten like it.

Another of the important benefits of fasting six days of Shawwaal is that is makes up for any shortfall in a person''s obligatory Ramadaan fasts, because no one is free of shortcomings or sins that have a negative effect on his fasting. On the Day of Resurrection, some of his naafil deeds will be taken to make up the shortcomings in his obligatory deeds, as the Prophet (peace and blessings of Allaah be upon him) said: “The first thing for which people will be brought to account on the Day of Resurrection will be their salaah (prayer). Our Lord, may He be glorified and exalted, will say to His angels – although He knows best – ‘Look at the salaah of My slave, whether it is complete or incomplete.’ If it is perfect, it will be recorded as perfect, and if something is lacking, He will say, ‘Look and see whether My slave did any voluntary (naafil) prayers.’ If he did some voluntary prayers, [Allaah] will say, Complete the obligatory actions of My slave from his voluntary actions.’ Then all his actions will be dealt with in a similar manner.” (Narrated by Abu Dawood).

When should a Muslim start fasting six days of Shawwaal?

You can start fasting six days of Shawwaal from the second day of Shawwaal, because it is haraam to fast on the day of Eid. You can fast the six days at any time during Shawwaal, although the best of good deeds are those which are done soonest.

These days do not have to be fasted immediately after Eid al-Fitr; it is permissible to start fasting them one or more days after Eid, and they may be done consecutively or separately during the month of Shawwaal, according to what is easier for a person. There is plenty of room for maneuver in this matter, and this is not obligatory, it is Sunnah.

Do the six days of Shawwaal have to be fasted consecutively?

It is not a necessary condition that they should be fasted consecutively. If you fast them separately or consecutively, it is OK. The sooner you do them, the better, because Allaah says (interpretation of the meanings): so compete in good deeds [al-Maaidah 5:48]

And march forth in the way (which leads to) forgiveness from your Lord [Aal Imran 3:133]

[Moosa peace be upon him said:] and I hastened to You, O my Lord, that You might be pleased [Ta-Ha 20:84]

And (you should hasten to fast these six days) because delaying may cause problems. This is the view of the Shaafa is and some of the Hanbalis, but it is OK if you do not hasten it and you delay it until the middle or end of the month.

Al-Nawawi (may Allaah have mercy on him) said: Our companions said: it is mustahabb to fast six days of Shawwaal. Because of this hadeeth they said: it is mustahabb to fast these days consecutively at the beginning of Shawwaal, but if one separates them or delays them until after Shawwaal, this is permissible, because he will still be following the general guidelines of the hadeeth. We have no dispute regarding this matter, and this was also the view of Ahmad and Dawood.

And Allah knows the best.