Hadith #2439 (Sunan Abi Dawud)
Book: Fasting (Kitab Al-Siyam)
Narrator(s): Hushab bin 'Aqil al-Jarmi حوشب بن عقيل الجرمي, Ikrama عكرمة, Sulaiman bin Harb سليمان بن حرب
Grade: Sahih

I never saw the Messenger of Allah (ﷺ) fasting during the first ten days of Dhu al-Hijjah.

Source: https://parallelquran.com/hadith/sunan-abi-dawud-2439/