The Prophet ﷺ said, ’There is no day on which Allah frees people from the Fire more so than on the Day of ‘Arafah. Indeed, He draws near and then boasts of them to the angels then says, “What do these want?“’ [Muslim]
Allah says in Qur'an:
Today I have perfected for you your religion and completed upon you My blessing and I have chosen for you Islam as [your] religion” (5:3)
This verse was revealed on the day of Arafah.
This is the most important ritual of the Hajj, without which the Hajj would be incomplete.The Prophet ﷺ said, ’Hajj is ‘Arafah’
Simply ,"The best day of the year is the Day of Arafah" [Ibn Ḥibbān]
So make sure that you take advantage of that Day, do lots of takbīr, du`ā,, etc