Musannaf Ibn Abi Shayba 3:5722

Yahya ibn Abi Bukayr narrated to us, from Shu'bah, from Mansur, from Ibn Sirin, regarding the verse: "And do not recite [too] loudly in your prayer, nor recite [too] quietly in it." He said: "It is better to be public, and it is permissible to be private." Regarding the verse: "And seek between that a way," he said: "You make them equal in privacy and publicity."