All perfect praise be to Allah, The Lord of The Worlds, and may His Peace and Blessings be upon our Prophet Muhammad and upon all of his family and companions.
It is recommended to fast on the Day of Arafah even if it falls on a Saturday because this is an exception to the dislike of singling out Saturday for fasting. The dislike of singling out Saturday is tied for offering voluntary fasting without a specific reason. However, if there is a reason for fasting, such as fasting every other day, fasting on the Day of Arafah, or fasting on the Day of Ashura, and if fasting any of which coincides with a Saturday, then fasting Saturday alone is not disliked.
The evidence for this is in both, the Sahihan (Bukhari and Moslim), whereas, Abdullah Ibn ‘Amr reported Allah's Messenger (PBUH) as saying: "The fasting dearest to Allah is David’s; he would fast on alternate days." [Agreed upon]. Therefore, anyone who fasts on alternate days his fast will fall on a Saturday later.
In this regard, Al-Imam Ar-Ramly (May Allah have mercy on his soul) stated: "It is disliked to single out Saturday... and this applies when it does not coincide with a habitual fast, such as fasting every other day, or fasting on Ashura or Arafah, and this coincides with his fast: then it is not disliked, similar to the case of fasting on the day of doubt. This was mentioned in Al-Majmu', and it is the apparent." [Nihayat Al-Muhtaj vol.3/pp.209].
The Day of Arafah is one of the best days in the Sight of Allah, The Exalted, and it has been encouraged to fast on this day. Besides, Prophet Muhammad (PBUH) said: "I seek from Allah that fasting on the day of Arafah may atone for the sins of the preceding and the coming years." [Moslim].
Therefore, it is recommended to fast on the Day of Arafah even if it falls on a Saturday, and doing so isn't disliked, whether a person fasts a day before it or not, because it is a voluntary fast related to a specific time. And Allah Knows Best.
