Matthew 6:5

Tertullian On Prayer

Do the ears of God wait for sound? How, then, could Jonah's prayer find way out unto heaven from the depth of the whale's belly, through the entrails of so huge a beast; from the very abysses, through so huge a mass of sea? What superior advantage will they who pray too loudly gain, except that they annoy their neighbours? Nay, by making their petitions audible, what less error do they commit than if they were to pray in public?[103]

Tertullian On Prayer

But how" in every place," since we are prohibited[161]

Didache

2. Neither pray as the hypocrites; but as the Lord commanded in His Gospel,[82]

Constitutions of the Holy Apostles Book VII

Now, "when ye pray, be not ye as the hypocrites; "[109]