Hazrat Anas bin Malik (May Allah be pleased with him) reported: The Messenger of Allah (PBUH) never proceeded (for the prayer) on the Day of Eid-ul-Fitr unless he had eaten some dates.
Hazrat Anas (May Allah be pleased with him) also narrated: The Prophet (PBUH) used to eat odd number of dates.
[Al-Bukhari Volume 2, Book 15, Number 73]