Mu'awiyah bin Yahya al-Sadafi narrated it from al-Zuhri, from Sa'id bin al-Musayyib, once from Sayyiduna Abu Sa'id and once from Sayyiduna Abu Hurayrah (may Allah be pleased with them both), from the Prophet (peace and blessings be upon him): "The days of Tashriq are all days of slaughter." In this chain he said: from Abu Sa'id.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / 19245