Salim (may Allah have mercy on him) narrates from Sayyiduna Ibn Umar (may Allah be pleased with them both), and Urwah (may Allah have mercy on him) from Sayyidah Aishah (may Allah be pleased with her), that they both said: "Fasting during the days of Tashriq was not permitted except for one who could not find a sacrificial animal."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8465