Matthew 6:9

Irenaeus Against Heresies Book II

That God is the Creator of the world is accepted even by those very persons who in many ways speak against Him, and yet acknowledge Him, styling Him the Creator, and an angel, not to mention that all the Scriptures call out [to the same effect], and the Lord teaches us of this Father[41]

Clement of Alexandria The Instructor Book I

And the Lord says in His prayer, "Our Father, who art in heaven."[172]

Fragments of Clement from the Latin Translation of Cassiodorus

For so you have in the Lord's prayer, "Hallowed be Thy name."[23]

Tertullian Against Praxeas

self looked up, and prayed, and made supplication of the Father; whither also He taught us to raise ourselves, and pray, "Our Father which art in heaven," etc.,[314]

Origen de Principiis Book II

Again, what else does the expression, which ought to be used by those who pray, "Our Father who art in heaven,"[35]

Cyprian Treatise IV On the Lord's Prayer

And forgive us our debts, as we forgive our debtors. And suffer us not to be led into temptation; but deliver us from evil. Amen."[16]

Archelaus Acts of the Disputation with the Heresiarch Manes

And to whom, then, did the Lord Jesus address Himself, when in these terms He taught men to pray: "When ye pray, say, Our Father which art in heaven; "[164]

Lactantius Divine Institutes Book IV

And it makes the entire difference what you worship, not how you worship, or what prayer you offer.[385]

Constitutions of the Holy Apostles Book III

ure, holy, beloved of God, the son of God, praying as a son to his father, and saying, as from the common congregation of the faithful, thus: "Our Father, which art in heaven, hallowed be Thy name; Thy kingdom come; Thy will be done on earth, as it is in heaven; give us this day our daily bread; and forgive us our debts, as we forgive our debtors; and lead us not into temptation, but deliver us from the evil one: for Thine is the kingdom, and the power, and the glory, for ever. Amen."[56]

Constitutions of the Holy Apostles Book VII

but as the Lord has appointed us in the Gospel, so pray ye: "Our Father which art in heaven, hallowed be Thy name; Thy kingdom come; Thy will be done, as in heaven, so on earth; give us this day our daily bread; and forgive us our debts, as we forgive our debtors; and lead us not into temptation, but deliver us from evil; for Thine is the kingdom for ever. Amen."[110]

Acts of the Holy Apostle Thomas

and not only hast Thou given us this, but hast also taught us how to pray;[52]