Sayyiduna Anas (may Allah be pleased with him) said: The Prophet (peace and blessings be upon him) came to Madinah, and the people of Madinah had two fixed days on which they used to play. He (peace and blessings be upon him) said: "I have come to you, and you had two days fixed from the time of Jahiliyyah on which you used to play. Allah has replaced them for you with better days: one is Eid al-Fitr and the other is Eid al-Adha."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة الخوف / 6123