[2.111.4] God also never taught the people to honour Him with lips and keep their hearts cold. But since Samuel prayed audibly in front of the people, equally so several of the prophets, and because David sang to God the Lord his psalms and Salmo his High Song, the people came to empty lip prayer and to cold sacrifices.

[2.111.5] However, before God such prayers and sacrifices are repulsive! Who cannot pray in the heart should rather not pray at all, so as to not behave improper before God. God did not give feet, hands, eyes, ears and lips to man to pray vainly and vacuously, but only the heart!