(22) باب النَّهْىِ عَنْ صَوْمِ، يَوْمِ الْفِطْرِ وَيَوْمِ الأَضْحَى
Abu Ubaid, the freed slave of Ibn Azhar, reported:
I observed Id along with Umar b. al-Khattab (Allah be pleased with him). He came (out in an open space) and prayed and (after) completing it addressed the people and said: The Messenger of Allah (ﷺ) has forbidden the observing of fast on these two days. One is the day of Fitr (at the end of your fasts), and the second one, the day when you eat (the meat) of your sacrifices.
Reference: Sahih Muslim 1137
In-book reference: Book 13, Hadith 177
USC-MSA web (English) reference(deprecated numbering scheme): Book 6, Hadith 2533