'A'isha and lbn 'Umar (RAA) narrated, 'Nobody was allowed to fast on the days of Tashriq except for those, who could not afford the Hadi (sacrifice).' Related by Al-Bukhari. (ID)
English reference (ID): Book 5, Hadith 708 (ID)
Arabic reference (ID): Book 5, Hadith 688 (ID)