Abu Dawud Book 2, Hadith Number 1130.

Narated By Anas ibn Malik : When the Apostle of Allah (PBUH) came to Medina, the people had two days on which they engaged in games. He asked: What are these two days (what is the significance)? They said: We used to engage ourselves on them in the pre-Islamic period. The Apostle of Allah (PBUH) said: Allah has substituted for them something better than them, the day of sacrifice and the day of the breaking of the fast.