Additions to the Lord's Prayer

qawe

Why do we add "through Jesus Christ our Lord, for thine is the kingdom, the power, and the glory forever and ever. amen."

And what is the source of this addition, and when did it occur historically?

Remnkemi

This is a matter of codicology. Different manuscripts include "for Thine is the Kingdom, the power and the glory forever Amen." and many do not include it. (I only examined Matthew 6:13)

In English,

NKJV: Included. NIV: Not included. RSV: Not include but included in a footnote. Young's: included. ASB: Included but includes a footnote stating it was not included in early manuscripts. 

In Arabic,

Smith Van Dyke: Included. Easy to Read Version: Included, Life application Bible: Included.

In Greek, 

1550 Stephanus NT: Included. 1881 Westcott-Hort: Not included. 1894 Scrivener: Included. SBL: Not included but included in a footnote.

In Coptic, 

Bohairica (Wells version based on Horner's Coptic NT): Not included. Coptic.org (allegedly from Dair Anba Bishoi): included. Sahidic Wells version: Included. 

I am also sure if I went through more Coptic manuscripts, we'll have some that include the addition, some that do not. This phenomenon is not exclusive to the Coptic New Testament.

Regarding "In Jesus Christ our Lord", this seems to be a Coptic addition that is liturgical, not necessarily scriptural. It is a reflection of Coptic piety (invoking the name of Christ and the name of the Cross in everything).