What the manuscripts show. Codex Sinaiticus, Codex Vaticanus, Codex Bezae and other early witnesses end the prayer with “deliver us from evil” (or “from the evil one”), and so does most of the Latin tradition; Origen’s text agrees. The doxology appears, with some variation in wording, in Codex Washingtonianus, in many later Greek manuscripts and the Byzantine tradition, and in Syriac and Sahidic Coptic witnesses. Luke’s shorter form of the prayer (Luke 11:2–4) has no doxology in any of the texts compared here. That the doxology was not part of Matthew’s earliest text is the common judgment of textual scholars (Strong).
But it is very early. The Didache, one of the earliest Christian church manuals outside the New Testament, gives the Lord’s Prayer and ends it, “for Yours is the power and the glory forever,” telling Christians to pray it three times a day. The fuller form echoes David’s prayer in 1 Chronicles 29:11: “thine is the kingdom, O LORD.” So the doxology is best understood as the Church’s ancient liturgical response to the prayer, which then came to be copied into Matthew (Strong).
What the Orthodox Church reads and prays. The Patriarchal Text prints the doxology as part of Matthew 6:13. In the Divine Liturgy, after the people pray the Our Father, the priest exclaims: “For thine is the kingdom, and the power and the glory, of the Father, and of the Son, and of the Holy Spirit, now and ever, and unto ages of ages.” The Orthodox Church thus keeps the doxology exactly where it seems to have begun: as the Church’s answer, voiced by the priest, to the prayer the Lord taught.
How translations handle it. The KJV, NKJV and Reina-Valera 1909 print it in Matthew. The Douay-Rheims, translated from the Vulgate, ends with “deliver us from evil. Amen.” The ESV, NIV, NRSVUE and RSV Catholic Edition put the doxology in a footnote.
What it does and does not change. Every phrase of the doxology is biblical, and its use in worship is attested very early, in the Didache. Whether it is printed in Matthew or in a note, Christians of every tradition may rightly pray it. The question is only where these words first stood: in Matthew’s pen or on the Church’s lips.