The Prophet (may Allah's peace and blessings be upon him) Abu Bakr, and ‘Umar used to offer the Eid prayers before delivering the sermon
Authentic hadithعن عبد الله بن عُمر رضي الله عنهما قال: «كان النبي صلى الله عليه وسلم وأبو بكر وعُمر يصلون العيدين قبل الخُطْبة».
‘Abdullāh ibn ‘Umar (may Allah be pleased with him) reported: The Prophet (may Allah's peace and blessings be upon him) Abu Bakr, and ‘Umar used to offer the Eid prayers before delivering the sermon.
Explanation
It was the habit of the Prophet (may Allah's peace and blessings be upon him) and the rightly guided caliphs to lead the Eid prayer in both Eid al-Fitr and Eid al-Ad'ha, then they would give the sermon. They would pray first then give the sermon, and Muslims kept doing so until Marwān's era came, so he rose over the pulpit and gave the sermon before the prayer.
Source · Narrated by Bukhari & Muslim
From the Hadith Encyclopedia (hadeethenc.com).