Sahih Muslim 886bBook 8, Hadith 6
وَحَدَّثَنِي مُحَمَّدُ بْنُ رَافِعٍ، حَدَّثَنَا عَبْدُ الرَّزَّاقِ، أَخْبَرَنَا ابْنُ جُرَيْجٍ، أَخْبَرَنِي عَطَاءٌ، أَنَّ ابْنَ عَبَّاسٍ، أَرْسَلَ إِلَى ابْنِ الزُّبَيْرِ أَوَّلَ مَا بُويِعَ لَهُ أَنَّهُ لَمْ يَكُنْ يُؤَذَّنُ لِلصَّلاَةِ يَوْمَ الْفِطْرِ فَلاَ تُؤَذِّنْ لَهَا - قَالَ - فَلَمْ يُؤَذِّنْ لَهَا ابْنُ الزُّبَيْرِ يَوْمَهُ وَأَرْسَلَ إِلَيْهِ مَعَ ذَلِكَ إِنَّمَا الْخُطْبَةُ بَعْدَ الصَّلاَةِ وَإِنَّ ذَلِكَ قَدْ كَانَ يُفْعَلُ - قَالَ - فَصَلَّى ابْنُ الزُّبَيْرِ قَبْلَ الْخُطْبَةِ .
As there is no Adhan on 'Id-ul-Fitr, so you should not pronounce it. Ibn Zubair did not pronounce Adhan on that day. He (Ibn 'Abbas) also sent him (with this message) that sermon (is to be delivered) after the prayer, and thus it was done. So lbn Zubair observed prayer before Khutba.