“The Messenger of Allah, may Allah’s peace and blessings be upon him, would not set out (for the prayer) on the Day of al-Fitr until he had eaten some dates, and he would eat them in an odd number (witr).”

Narrated by al-Bukhārī (No. 953), from the ḥadīth of Anas, may Allah be pleased with him.

Brief Explanation of the Hadith

 The Companions — may Allah be pleased with them — were keen to transmit the guidance of the Prophet — may Allah’s peace and blessings be upon him — in his actions and stillness, so that they might emulate him. Among this is what they transmitted regarding his practice before going out to the ʿĪd prayer.
In this ḥadīth, Anas ibn Mālik, may Allah be pleased with him, reports that the Prophet — may Allah’s peace and blessings be upon him — “would not set out (for the prayer) on the Day of al-Fitr until he had eaten some dates,” that is, before going out to the musallā (prayer ground). Al-ghuduww refers to going out at the beginning of the day.
He would eat them in an odd number (witr), that is, three, five, or a similar odd quantity, because Allah — Exalted is He — is One and loves odd numbers, and it also signifies His Oneness. It is easier to consume, more quickly beneficial, and suits the sweetness appropriate after a fast. If dates were unavailable, he would break the fast with water or something else.
The wisdom behind eating before going out on the day of Fitr is to manifest the breaking of the fast and to distinguish it from a day of fasting, so that it would not be mistaken as a continuation of the fast.