Assalmu Alaikum,
Fasting on the day of Arafah is an expiation the sins for two years.:
The ninth day of Dhul-Hijjah is the day of ’Arafah, since it is on this day that the pilgrims gather at the mountain plain of ’Arafah, praying and supplicating to their Lord. It is mustahabb (highly recommended) for those who are not pilgrims to fast on this day.
The
Prophet (sallallaahu ’alayhi wa sallam) was asked about fasting on the
day of ’Arafah, so he said, “It expiates the sins (Minor) of the
past year and the coming year.”
-[Muslim
(no. 1162)]
Not everyone can go on Hajj, and certainly not every year, but this Day of
Arafa is one of the great gifts of Allah (subhana wa ta'ala) that people all
over the world can benefit from. On this day, Allah (subhana wa ta'ala) grants
fasting Muslims forgiveness for their faults of two years, if they have
committed any, if not, Allah (subhana wa ta'ala) elevates their degree in
Paradise.
Make a note of this day on your calendar, so that you remember to celebrate it
by fasting and making dhikr, dua and istighfar.
---
It
is Sunnah to recite takbeer (saying Allaahu akbar (Allaah is most great)),
tahmeed (saying al-hamdu Lillah (praise be to Allaah)), tahleel (saying Laa
ilaaha ill-Allaah (There is no god but Allaah)) and tasbeeh (saying
Subhaan-Allaah (Glory be to Allaah)), during the first ten days of
Dhu’l-Hijjah, saying these words out loud in the mosques, homes, streets
and every place in which it is permissible to remember Allaah, to perform this
act of worship openly and proclaim the greatness of Allaah.
Men should recite out loud and women should recite quietly.
Allaah akbar, Allaahu akbar, laa
ilaaha ill-Allaah, Allaahu akbar, wa Lillaah il-hamd
(Allaah
is Most Great, Allaah is Most Great, there is no god but Allaah; Allaah is Most
Great and to Allaah be praise).