By reason of great humility the Lord did not appear as an angel but as a man, (Ὁ Κύριος, διὰ πολλὴν ταπεινοφροσύνην, οὐχ ὡς ἄγγελος ὤφθη, ἀλλ' ὡς ἄνθρωπος) and when he appeared in glory to the apostles on the Mount (Καὶ ὅτε ἐν δόξῃ ὤφθη τοῖς Ἀποστόλοις ἐπὶ τοῦ Ὄρους) he did not do it for his own sake when he showed himself (οὐ δι' ἑαυτὸν ἐποίησεν, δεικνὺς ἑαυτόν), but for the sake of the Church which is “the elect race,” (ἀλλὰ διὰ τὴν Ἐκκλησίαν, ἥτις ἐστὶ "τὸ γένος τὸ ἐκλεκτόν") that it might learn his advancement after his departure from the flesh (ἵνα μάθῃ τὴν προκοπὴν αὐτοῦ μετὰ τὴν ἐκ τῆς σαρκὸς ἔξοδον). For on high, too, he was Light and that which was manifest in the flesh and appeared here is not later than that above nor was it curtailed (Αὐτὸς γὰρ καὶ ἄνω Φῶς ἦν, καὶ ἐστὶ τὸ "ἐπιφανὲν ἐν σαρκὶ" καὶ τὸ ἐνταῦθα ὀφθὲν οὐχ ὕστερον τοῦ ἄνω), in that it was translated hither from on high, changing from one place to another, so that this was gain here and loss there ( οὐδὲ διεκέκοπτο ᾗ ἄνωθεν μετέστη δεῦρο, τόπον ἐκ τόπου ἀμεῖβον, ὡς τὸν μὲν ἐπιλαβεῖν, τὸν δὲ ἀπολιπεῖν)· . But he was the Omnipresent, and is with the Father (ἀλλ' ἦν τὸ πάντῃ Ὂν καὶ παρὰ τῷ Πατρὶ κἀνταῦθα), even when here, for he was the Father's Power (δύναμις γὰρ ἦν τοῦ Πατρός). And besides, it was necessary that that word also which the Saviour spoke should be fulfilled ( Ἄλλως τε ἐχρῆν κἀκεῖνον πληρωθῆναι τὸν λόγον τοῦ Σωτῆρος ὃν εἶπεν), “There are some of those standing here who will not taste death until they see the Son of Man in glory.” ("Εἰσί τινες τῶν ὧδε ἑστηκότων, οἳ οὐ μὴ γεύσονται θανάτου, ἕως ἂν ἴδωσι τὸν Υἱὸν τοῦ Ἀνθρώπου ἐν δόξῃ") Therefore, Peter and James and John saw and fell asleep. (Εἶδον οὖν καὶ ἐκοιμήθησαν ὅ τε Πέτρος καὶ Ἰάκωβος καὶ Ἰωάννης)
[Exerpta ex Theodoto 4]
But Mark 9:
Compare1And Jesus was saying to them, "Truly I say to you, there are some of those who are standing here who will not taste death until they see the kingdom of God after it has come with power." 2Six days later, Jesus took with Him Peter and James and John, and brought them up on a high mountain by themselves. And He was transfigured before them ...
with Theodotos's gospelMark 9:1 "1Καὶ ἔλεγεν αὐτοῖς· ἀμὴν λέγω ὑμῖν ὅτι εἰσίν τινες ὧδε τῶν ἑστηκότων οἵτινες οὐ μὴ γεύσωνται θανάτου ἕως ἂν ἴδωσιν τὴν βασιλείαν τοὺ θεοὺ ἐληλυθυῖαν ἐν δυνάμει."
Matthew 16:28 ἀμὴν λέγω ὑμῖν ὅτι εἰσίν τινες τῶν ὧδε ἑστώτων οἵτινες οὐ μὴ γεύσωνται θανάτου ἕως ἂν ἴδωσιν τὸν υἱὸν τοῦ ἀνθρώπου ἐρχόμενον ἐν τῇ βασιλείᾳ αὐτοῦ.
Luke 9:27λέγω δὲ ὑμῖν ἀληθῶς, εἰσίν τινες τῶν αὐτοῦ ἑστηκότων οἱ οὐ μὴ γεύσωνται θανάτου ἕως ἂν ἴδωσιν τὴν βασιλείαν τοῦ θεοῦ.
This IMO shows quite clearly that the canonical gospels were deliberately constructed to counter the earlier heretical arguments and understanding about Jesus. Theodotos gives the sense that Jesus says 'some of you will see me in glory' referring to a future (rather than immediate) reference to his glorification (after the resurrection). Then the editor of the canonical gospels (Irenaeus) changed it to make it about something else (the coming of the kingdom) and made it immediate i.e. in the next breath.Εἰσί τινες τῶν ὧδε ἑστηκότων, οἳ οὐ μὴ γεύσονται θανάτου, ἕως ἂν ἴδωσι τὸν Υἱὸν τοῦ Ἀνθρώπου ἐν δόξῃ