It is narrated from Abu Ubaidah, the freed slave of Ibn Azhar (may Allah have mercy on him), that I saw Sayyiduna Ali (may Allah be pleased with him) and Sayyiduna Uthman (may Allah be pleased with him) performing the Eid al-Fitr and Eid al-Adha prayers. After the prayer, they would advise the people, and I heard them say that the Messenger of Allah (ﷺ) forbade fasting on these two days.
Hadith Referenceالسنن المأثورة / باب صلاة العيدين / 168
Hadith Takhrijمسند احمد : 489/1، رقم : 435 وقال الارنوؤط: اسناده شرط مسلم صحيح