It was probably added by a copyist that used to hear this doxology in the celebration of the Eucharist just after the Our Father. Today you can still find it in the same place in the
Divine Liturgy of St. John Chrysostom, where it is said by the priest after the people have recited the Our Father:
á½Ï„ι σοῦ á¼ÏƒÏ„ιν ἡ βασιλεία καὶ ἡ δÏναμις καὶ ἡ δόξα, τοῦ ΠατÏὸς καὶ τοῦ Υἱοῦ καὶ τοῦ Ἁγίου ΠνεÏματος, νῦν καὶ ἀεὶ καὶ εἰς τοὺς αἰῶνας τῶν αἰώνων.
As you can see, later a reference to the Trinity was also added.
