I never saw the Messenger of Allah (ﷺ) fasting during the first ten days of Dhu al-Hijjah.
Sunan Abi Dawud Book 14, Hadith 127
← Previous Hadith The Messenger of Allah (ﷺ) as saying: There is no virtue more to the liking of Allah in any day than in these days, that is, the first ten days of Dhu al-Hijjah. They (the Companions) asked: Messenger of Allah, not even the struggle in the path of Allah (Jihad) ? He said: (Yes), not even the struggle in the path of Allah, except a man who goes out (in the path of Allah) with his life and property, and does not return with any of them.

Sunan Abi Dawud Book 14, Hadith 126 Next Hadith → Ikrimah said: We were with AbuHurayrah in his house when he narrated to us: The Messenger of Allah (ﷺ) prohibited fasting on the day of Arafah at Arafah.

Sunan Abi Dawud Book 14, Hadith 128