Dought & clear, - The virtue of fasting ‘Ashoora’

I heard that fasting the day of 'Ashoora' expiates for the past year,
is this true?
Does it expiate for everything, even major sins? What is the reason
for venerating this day?.
Praise be to Allah
Firstly:
Fasting the day of 'Ashoora' does expiate for the past year, because
the Prophet(peace and blessings of Allaah be upon him) said: "Fasting
the day of 'Arafah I hope Allaah will expiate thereby for the year
before it and the year after it, and fasting the day of 'Ashoora' I
hope Allaah will expiate thereby for the year that came before it."
Narrated by Muslim, 1162. This is by the bounty that Allaah bestows
upon us, whereby fasting one day expiates for the sins of a whole
year. And Allaah is the Owner of great bounty.
The Prophet(peace and blessings of Allaah be upon him) used to be very
keen to make sure he fasted on the day of 'Ashoora' because of its
great status. It was narrated that Ibn 'Abbaas (may Allaah be pleased
with him) said: I never saw the Prophet(peace and blessings of Allaah
be upon him) so keen to make sure he fasted any day and preferring it
over another except this day, the day of 'Ashoora', and this month –
meaning Ramadaan. Narrated by al-Bukhaari, 1867.
What is meant by being keen to make sure he fasted it is so as to earn
its reward.
Secondly:
With regard to the reason why the Prophet(peace and blessings of
Allaah be upon him) fasted on the day of 'Ashoora' and urged the
people to do likewise is mentioned in the hadeeth narrated by
al-Bukhaari (1865) from Ibn 'Abbaas (may Allaah be pleased with him),
who said: The Prophet(peace and blessings of Allaah be upon him) came
to Madeenah and saw the Jews fasting on the day of 'Ashoora'. He said,
"What is this?" They said, "This is a good day, this is the day when
Allaah saved the Children of Israel from their enemy and Moosa fasted
on this day." He said, "We are closer to Moosa than you." So he fasted
on this day and told the people to fast.
The words "this is a good day" – according to a version narrated by
Muslim, "This is a great day when Allaah saved Moosa and his people
and drowned Pharaoh and his people."
The words "so Moosa fasted on this day" – Muslim added in his report:
"In gratitude to Allaah, so that is we fast on this day."
According to another version narrated by al-Bukhaari, "So we fast it
out of respect for it."
The words "and told the people to fast" – according to another version
narrated by al-Bukhaari, "He said to his companions, 'You are closer
to Moosa than them, so fast this day."
Thirdly:
The expiation of sins that is achieved by fasting 'Ashoora' refers to
minor sins; with regard to major sins, they need separate repentance.
Al-Nawawi (may Allaah have mercy on him) said:
Fasting the day of 'Arafaah expiates for all minor sins, in othr words
this brings forgiveness for all sins except for major sins.
Then he said:
Fasting the day of 'Arafaah is an expiation for two years, and the day
of 'Ashoora is an expiation for one year, and if a person's Ameen
coincides with the Ameen of the angels, his previous sins will be
forgiven… Each of the things mentioned may bring expiation. If he does
something that expiates for minor sins he will be expiated, and if
there are no minor or major sins, it will be recorded for him as good
deeds and he will rise in status thereby… If there is one or more
major sins and no minor sins, we hope that it will reduce his major
sins.Al-Majmoo' Sharh al-Muhadhdhab, part 6.
Shaykh al-Islam Ibn Taymiyah (may Allaah have mercy on him) said: The
expiation of purification, prayer, and fasting Ramadaan, 'Arafah and
'Ashoora' applies to minor sins only.Al-Fataawa al-Kubra, part 5.