Protestants commonly end the Lord’s Prayer with the doxology, “For thine is the kingdom, the power, and the glory, forever and ever, Amen.” This is the ending given in the old King James version of the Bible (Mt. 6:13). The sentiment which these words so beautifully express is indeed an admirable one, filled with reverence and homage for the infinite God, worthy of all praise and glory. The Catholic Church does not find fault with the words nor the sentiment. She does not use them, however, for the simple reason that they were not spoken by our Lord when he gave us the Lord’s Prayer.
In the new Order of the Mass the Lord’s Prayer is given great prominence. The priest introduces the prayer, and with all standing, they recite the Lord’s Prayer. The priest then continues: “Deliver us, Lord…”. The doxology: “For the kingdom, the power, and the glory, are yours, now and forever”, is then acclaimed by the congregation.
In Eastern rites a similar doxology is added to the Our Father, e.g., in the Byzantine liturgy the words: “For thine is the kingdom and the might and the glory, Father, Son, and Holy Spirit, now and forever, and world without end,” has been added, of which a variation is usual among Protestants. Such an addition is already noted in the Didache, concerning prayer:
“Do not pray as the hypocrites either, but pray as the Lord commanded in His Gospel: Our Father, who 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 trespasses, as we forgive those who trespass against us; and lead us not into temptation, but deliver us from the evil one; for thine is the power and the glory unto ages of ages. Pray this way three times each day”.