Arafah

"Fasting the day of arafat expiates the sins of two years: a past one and a coming one."
                                                                                                                              (Muslim)

The Prophet (S.A.W) said: "The best Dua is the dua of Arafat"
                                                                                      (Tirmidhi)

Arafah has been classified as the best day of the year according to some scholars.