Musannaf Ibn Abi Shayba 3:3392

Abu Bakr narrated to us, he said: Abu al-Ahwas narrated to us, from Abu Ishaq, from al-Harith, from Ali. He said: When he used to recite in the two Eids, he would let those who were next to him hear, and he would not recite aloud with that [loud] recitation.