Anas ibn Malik reported: The Messenger of Allah ( peace and blessings be upon him) arrived in Medina during the two days they were celebrating.
The Prophet asked, “What are these two days?”
They said, “We would celebrate these two days in the time of ignorance.”
The Prophet said, “Verily, Allah has replaced these two days with two better days: Eid al-Adha and Eid al-Fitr.”
Source: Sunan Abī Dāwūd 1134
Happy Eid, everyone! كل عام و انتم بخير (May every year find you in good health)