Abu Dawud

Benefits and Issues:
➊ The ninth day of Dhu al-Hijjah, on which the standing at Arafat (wuquf ‘Arafat) takes place, is called the Day of Arafah.

➋ This hadith is weak.
Therefore, prohibition is not established from it.
However, since the pilgrims are occupied with the standing at Arafat and engaged in supplication and devotion during this time, for them this act is preferable to fasting.
For non-pilgrims, the virtue of fasting on this day is established, as has already been mentioned previously.
(Hadith: 2425)

Benefit:
In the aforementioned hadith, the prohibition of fasting on the Day of Arafah is established, but this is specific to the pilgrims (hujjaj), as the Prophet sallallahu alayhi wa sallam forbade the pilgrims from fasting on this day. Just as the Messenger of Allah sallallahu alayhi wa sallam himself did not fast on the Day of Arafah during the Farewell Pilgrimage (Hajjat al-Wada‘). (Sahih al-Bukhari, Book of Fasting, Chapter: Fasting on the Day of Arafah, Hadith: 1988)
Furthermore, the pilgrims are required to stand (wuquf) at Arafat and remain engaged in supplication and devotion during this time; therefore, this act takes precedence over fasting. For non-pilgrims, the virtue of fasting on this day is established from previous ahadith.

566 Benefits and Issues:
➊ Imam ‘Aqili rahimahullah declared this narration as munkar (rejected) because its narrator, Hawshab bin ‘Aqil, narrated this hadith from Mahdi bin Harb Hijri. ‘Aqili said that no one has followed up (mutaba‘ah) Hawshab in this narration. And the narrator who reports from him is also disputed. However, this objection holds no weight because most of the hadith scholars rahimahullah have declared Hawshab trustworthy (thiqah), and the judgment of Hafiz Ibn Hajar rahimahullah in "Taqrib al-Tahdhib" is also that he is trustworthy (thiqah). As for Mahdi Hijri, Imam Ibn Ma‘in said, “I know him.” But Imam Hakim rahimahullah declared his hadith authentic (sahih), and Hafiz Dhahabi rahimahullah supported him in "Talkhis al-Mustadrak." Imam Ibn Khuzaymah rahimahullah also declared it authentic, and Ibn Hibban rahimahullah mentioned him among the trustworthy (thiqaat), and Hafiz Ibn Hajar rahimahullah called him “maqbul” (acceptable). And the narrator who reports from him is Hawshab bin ‘Abdil, whom Hafiz Ibn Hajar rahimahullah called trustworthy (thiqah) in "Taqrib al-Tahdhib."
➋ This hadith is evidence that it is forbidden (haram) for the pilgrim (haji) to fast on the Day of ‘Arafah while at ‘Arafat. This is also the position of Imam Yahya bin Sa‘id al-Ansari. This is supported by the hadith of ‘Uqbah bin ‘Amir radi Allahu anhu in Sunan al-Nasa’i and others: “The Day of ‘Arafah is our day of Eid.” That is, for the people of ‘Arafah, this is a day of Eid. [سنن النسائي الحج ، باب النهي عن صوم ، يوم عرفة ، حديث : 3007] Therefore, they are prohibited from fasting on this day. However, according to the majority, not fasting is recommended (mustahabb).
➌ The Prophet sallallahu alayhi wa sallam also did not fast on the Day of ‘Arafah during the Farewell Pilgrimage (Hajjat al-Wada‘). *