Here is an interesting article:
Is the Doxology to the Lord's Prayer in Matthew 6:13 a late addition?
"For thine is the kingdom, and the power, and the glory, for ever. Amen."
This powerful doxology to the Lord's prayer has been falsely characterized as a late addition on the basis of just TWO manuscripts which are earlier by just ONE or a HALF century. The two earliest witnesses of Matthew 6:13, Sinaiticus (4th century) and Vaticanus (4th century), omit the doxology. The third earliest witness of Matthew 6:13, Codex Washingtonensis (4th/5th century) includes the doxology. Despite there being other witnesses testifying against the inclusion of the doxology, the earliest witness that does testify for its inclusion is predated by only two witnesses that are earlier by not even a full century. The doxology exists in the majority of Byzantine texts.
Codex Washingtonensis is housed at the Freer Gallery, Sackler Museum, Smithsonian Institution, Washington D.C. and the passage of the Lord's Prayer can be viewed at the website of The Center for the Study of New Testament Manuscripts:
Manuscript GA 032 - CSNTM
Since uncials can be difficult to read, a photograph of the leaf containing the Lord's Prayer has been reproduced here (for nonprofit educational fair use purposes) with the prayer underlined and the doxology in particular underlined in blue. The words of the Lord's Prayer in Codex Washingtonensis matches the words of the Textus Receptus word for word, letter by letter for the most part.
Please click on the image to see the full size view
John Chrysostom (347–407) expounded the doxology in his homily, Homily 19 on St. Matthew, at paragraph 10 [Download a PDF of the Lord's Prayer portion of the Homily HERE]. Surely, this 4th century Archbishop of Constantinople would have had earlier manuscripts than what we have today.
The omission of the doxology could be sufficiently explained as an early attempt to harmonize the prayer in Matthew 6:9-13 with another version of the Lord's prayer in Luke 11:2-4. If the doxology were added later, there should be versions of the prayer in Luke with the doxology. Such cannot be found in the body of manuscript evidence.
Sources:
Nestle-Aland: Novum Testamentum Graece, 27th revised edition (2006).
The Center for the Study of New Testament Manuscripts (
http://images.csntm.org/Manuscripts/GA_032/CodexW_016a.jpg)
Link:
Is the Doxology to the Lord's Prayer in Matthew 6:13 a late addition? - King James Version Today