Question:  What is the ruling with regards to fasting on the day of Arafah?

Answer:  It is Sunnah to fast on the day of Arafah.  The Messenger Sallallahu Alaihi Wasallam said: ““Fasting on the day of ‘Arafah absolves the sins for two years: the previous year and the coming year”. [Muslim]

And Allah Knows Best