Concerning matthew 6:13, John Gill has this to say, "For thine is the kingdom, and the power, and the glory, for ever, Amen. This conclusion is left out in the Arabic and Vulgate Latin versions, as it is in #Lu 11:4. It stands thus in the Jewish prayers {d},
“ayh Klv twklmh yk, "for the kingdom is thine", and thou shalt reign in glory for ever and ever.”
The usual response at the close of prayers, and reading the Shema, instead of "Amen", was {e} this:
“Blessed be the name of the glory of his kingdom, for ever and ever.”
Which bears some resemblance to this concluding expression, which ascribes everlasting kingdom, power, and glory, to God: which may be considered either as a doxology, or an ascription of glory to God, which is his due; and ought be given him in all our prayers to him; or as so many reasons strengthening our faith in prayer; or as many arguments with God, with respect to the petitions made; since the kingdom of nature, providence, grace, and glory, is his: he is omnipotent, he has power to give us our daily bread; to forgive our sins; to preserve from, support under, and deliver out of temptation; to keep from all evil, and preserve from a total and final falling away: whose glory is concerned in all, to whom the glory of all is, and to whom it must, and shall be given; and all this for ever: and the whole is concluded with the word "Amen"; which is a note of asseveration, of the truth herein contained; is added by way of assent to every petition made; is expressive of an hearty wish, and desire to have all fulfilled; and also of faith and confidence, that they will be answered. And this word being retained, and kept the same in all languages, signifies the unity of the spirit, and faith in prayer, in all the saints, in all ages. I leave this prayer with one observation, and that is, whereas it has been so long, and so often said, that this is the Lord’s prayer, it can never be proved that he ever made use of it; and it is certain that he did not make it, as appears from what has been cited out of the Jewish records: the several petitions in it were in being and use before he directed to them; and not only the petitions, but even the very preface and conclusion, are manifestly of Jewish original: what our Lord did was, he took the most proper and pertinent petitions, that had been used by good men among that people; which, with some alterations much for the better, he put together in this order, and gave his approbation of; and that with this view, to point out to his disciples some of the best and most suitable petitions to be made; and to give them a pattern of brevity and conciseness in prayer; and teach them to pray after such a manner, or in some such like words and expressions. This I observe, not to lessen the usefulness of this excellent pattern of sound words; the whole, and every part of it, being exceedingly instructive, and worthy of imitation; but to rectify a vulgar mistake, and to abate the formal and superstitious observance of it.
{a} Seder Tephillot, fol. 3. 1. Ed. Basil. fol. 4. 2. Ed. Amstelod. Shaare Zion, fol. 73. 1. T. Bab. Beracot, fol. 60. 2.
{b} T. Bab. Beracot, fol. 60. 2.
{c} Ib. fol. 16. 2.
{d} Seder Tephillot, fol. 280. 1. Ed. Basil.
{e} Misn. Yoma, c. 4. sect. 1. & 6. 2. T. Bab. Pesachim, fol. 56. 1. & Taanith, fol. 16. 2. Seder Tephillot, fol. 70. 2. Ed. Basil. "
Seems it is indeterminate to see whether this was in every MSS and it would be a "red herring" to try and push the issue farther than that, BUT, it is common sense that the Jewish Messiah/ Jesus Christ, would certainly use this phrase in His example to other Jews on how to pray to their Father in Heaven. Who would ever think that this inclusion would be looked down upon for the lack of some available MSS to support it.
Makes one wonder why the objection of it's inclusion, especially when it's His Kingdom, His Power and His Glory we're talking about.
Good reply Sister Michelle!