Sahih Bukhari Volume 2, Book 13, Hadith 960

قَالَ وَأَخْبَرَنِي عَطَاءٌ، أَنَّ ابْنَ عَبَّاسٍ، أَرْسَلَ إِلَى ابْنِ الزُّبَيْرِ فِي أَوَّلِ مَا بُويِعَ لَهُ إِنَّهُ لَمْ يَكُنْ يُؤَذَّنُ بِالصَّلاَةِ يَوْمَ الْفِطْرِ، إِنَّمَا الْخُطْبَةُ بَعْدَ الصَّلاَةِ‏

Ata told me that during the early days of Ibn Az-Zubair, Ibn Abbas had sent a message to him telling him that the Adhan for the 'Id Prayer was never pronounced (in the life time of Allah's Apostle) and the Khutba used to be delivered after the prayer.