Dought & clear - The virtue of fasting six days of Shawwaal

What is the ruling on fasting six days of Shawwaal? Is it waajib (obligatory)?
Praise be to Allaah.
Fasting six days of Shawwaal after the obligatory fast of Ramadaan
isSunnah Mustahabbah, not waajib. It is recommended for the Muslim to
fast six days ofShawwaal, 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 hehad 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 itwith six days of Shawwaal, it
will be as ifhe 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
thiswhen 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
alsoSaheeh al-Targheeb wa'l-Tarheeb, 1/421).It was also narrated by
IbnKhuzaymah with the wording: "Fasting for the month of Ramadaan
brings the reward of tenlike it, and fasting for sixdays brings the
reward of two months, and that is the fasting of the whole year."
The Hanbali and Shaafa'ifuqaha' explained that fasting six days of
Shawwaal after fasting Ramadaan makes it as if one has fasted for an
entire year of obligatoryfasts, 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
negativeeffect on his fasting. On the Day of Resurrection, some of his
naafil deeds will be taken to make upthe 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).
OurLord, 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 didany 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 similarmanner."(Narrated by Abu Dawood).
And Allaah knows best.