Because the "Lord's Prayer" doxology is part of Matthew's Gospel (6:13), we are blessed to have numerous ancient copies. As best I can work out, is a complete list of documents (MSS) that contain this part of the record up to the 13th century.
Diatessaron (2nd) omit, copmeg (3rd) omit, Origen (3rd) omit, Tertullian (3rd) omit, Cyprian (3rd) omit, 01 (4th) omit, 03 (4th) omit, ita (4th) omit, syrc (4th) include, Cyril-J (4th) omit, Gregory-N (4th) omit, vg (400) omit, Ambros’r (400) omit, Ambrose (400) omit, itk (400) include, 05 (5th) omit, itb (5th) omit, ith (5th) omit, Cyril (5th) omit, Chromatius (5th) omit, Jerome (5th) omit, 032 (5th) include, syrp (5th) include 0233 (500) include, 035 (6th) omit, 042 (6th) include, itf (6th) include, syrpal (6th) include, 0170 (500) omit, itq (600) include, itaur (7th) omit, syrh (7th) include, itl (8th) omit, 07 (8th) include, 011 (9th) include, 019 (8th) include, 037 (9th) include, 038 (9th) include, 33 (9th) include, 565 (9th) include, 892 (9th) include, 1424 (900) include, f1 (10th-14th) omit, f13 (11-15) include, l 547 (13th) omit.
Note, I have not included the Didache because the text there only says:
Ὅτι σοῦ ἐστιν ἡ δύναμις καὶ ἡ δόξα εἰς τοὺς αἰῶνας.
and NOT
Ὅτι σοῦ ἐστιν ἡ βασιλεία καὶ ἡ δύναμις καὶ ἡ δόξα εἰς τοὺς
αἰῶνας. Ἀμήν.
From this list we con observe the following:
- The earliest MSS in Greek omit the doxology until the 5th century
- The earliest Patristic writings also omit it.
- The doxology appears first in the Syriac and only later in the Itala versions
- Jerome's Vulgate (400) omits it.
- The doxology became prominent in the Byzantine tradition
- Luke omits the doxology but Luke's version is even shorter by omitting the prayer for deliverance from the evil one.
For all these reasons, UBS5 regards the omission of the doxology in the original text as {A} = almost certain. Further, the earliest recorded forms of this doxology occur in a variety of forms before it became standardized in its triple strophic form.
Bruce Metzger (In his Textual commentary on the GNT) suggests that the doxology was gradually added to
"adapt the Prayer for liturgical use in the early church. Still later
scribes added, "of the Father and of the Son and of the Holy Spirit".