Sunan an-Nasa'i, Volume 2, Book 19, Hadith 1570 (DarusSalam) ⓘ
It was narrated that 'Ata said: "I heard Ibn 'Abbas say: 'I bear witness that I attended 'Eid with the Messenger of Allah; he started with the prayer before the Khutbah, then he delivered the Khutbah.'"
أَخْبَرَنَا مُحَمَّدُ بْنُ مَنْصُورٍ، قَالَ حَدَّثَنَا سُفْيَانُ، قَالَ سَمِعْتُ أَيُّوبَ، يُخْبِرُ عَنْ عَطَاءٍ، قَالَ سَمِعْتُ ابْنَ عَبَّاسٍ، يَقُولُ أَشْهَدُ أَنِّي شَهِدْتُ الْعِيدَ مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم فَبَدَأَ بِالصَّلاَةِ قَبْلَ الْخُطْبَةِ ثُمَّ خَطَبَ .
also referenced under: Hadith 1569 (Reference) & Book 19, Hadith 14 (In-Book)