Is it Sunnah to abstain from food and drink from Fajr until the completion of the Eid prayer on Eid al-Adha, and if it is Sunnah, is it for Eid al-Fitr or Eid al-Adha?

The Sunnah is that a person should not eat anything on the day of Eid al-Adha until he prays the Eid prayer, and that he should eat something on the day of Eid al-Fitr before going out for the prayer. It is best that this be dates, for "he [the Prophet] would not go out on the day of Eid al-Fitr until he had eaten, and he would not eat on the day of Eid al-Adha until he had prayed," and "he would not go out on the day of Eid al-Fitr until he had eaten some dates."