Abu Sa'id Al-Khudri (RAA) narrated. 'The Messenger of Allah (ﷺ) has prohibited fasting on two days; the day of Fitr (breaking the fast of Ramadan) and on the day of sacrifice ('Idul Adha).' Agreed upon. (IT)
English reference (IT): Book 5, Hadith 706 (IT)
Arabic reference (IT): Book 5, Hadith 686 (IT)