"'When you have lifted up the Son of man, then you will know that I am [(τότε γνώσεσθε ὅτι ἐγω εἰμι)]. . . .'"
Jn 8:28, RSV, but with the concluding pronoun, i.e. "he" ("then you will know that I am he"), removed. Cf. the LXX of Is 43:10: "I too am a witness, says the Lord God, and the servant whom I have chosen so that you may know and believe and understand that I am [(ἵνα γνῶτε...ὅτι ἐγώ εἱμι)]" (NETS). The pronoun is there in the Hebrew of v. 10 ("that I [am] He [(כִּֽי־אֲנִי הוּא)]"), but that is followed by v. 11: "I, I am the Lord [(אָנֹכִי אָנֹכִי יְהוָה, ἐγὼ ὁ Θεός)]". All of this is brought out on pp. 347-349 (pp. 345 ff.) of Joseph Ratzinger's Jesus of Nazareth: from the baptism in the Jordan to the transfiguration, trans. Adrian J. Walker (New York, NY: Doubleday, 2007), whence the heading, which occurs on p. 349.