Musannaf Ibn Abi Shayba 3:5717

Abu Khalid al-Ahmar narrated to us, from al-Hajari, from Abu Iyad, who said: When the Prophet (peace and blessings of Allah be upon him) used to pray at the House (the Kaaba), he would recite aloud, and the polytheists would harm him. Then was revealed: "And do not recite [too] loudly in your prayer, nor recite too quietly," [up to] the end of the verse.