John 7:8

ὑμεῖς ἀνάβητε εἰς τὴν ἑορτήν· ἐγὼ οὔπω ἀναβαίνω εἰς τὴν ἑορτὴν ταύτην, ὅτι ὁ ἐμὸς καιρὸς οὔπω πεπλήρωται (John 7:8 WH).

The reading οὔπω in Jn 7:8 "was introduced at an early date (it is attested by P66, 75) in order to alleviate the inconsistency between ver. 8 and ver. 10" (Bruce Metzger, A Textual Commentary).

However, Ernst Haenchen in his commentary on John seems to think that οὔπω is original (See Haenchen, John 2:7).

He reasons: "If Jesus does not know when his time is fulfilled and the Father calls him to Jerusalem (to die?) then logically he cannot say 'not,' but must say, as in v 6, 'not yet.' "

Even if οὐκ ("not") is less than original, and we cannot be positively sure at this time which reading is correct, John's use of οὐκ still does not mean that Jesus lied. A.T. Robertson points out that Jesus "did not change his plans . . . He simply refused to fall in with his brothers' sneering proposal for a grand Messianic procession with the
caravan on the way to the feast" (Word Pictures in the NT).

"the more definite--and more difficult--reading, 'I am not going,' is undoubtedly the correct one. Jesus is represented as clearly refusing his brothers' proposal. He will not go to this festival at their request or initiative but only as his Father directs" (J.R. Michaels, John, 127).

Robert Mounce concurs: "The NIV follows the inferior textual tradition that reads oupō ('not yet') rather than ou ('not'), thus alleviating the apparent inconsistency with v. 10 in which Jesus does go to Jerusalem. It is better to follow the shorter text (so NASB) and understand Jesus as saying no more than he will not be going up to the Feast at that specific time (i.e., with his brothers). He is simply turning down their request— not promising that he will not go to the Feast a bit later when the time is right. Having turned down the advice of his brothers, Jesus remains for a time in Galilee."

Mounce, Robert H. John (The Expositor's Bible Commentary) (Kindle Locations 4043-4047). Zondervan. Kindle Edition.

Another Johannine scholar insists: "He refuses in the plainest terms to comply with human--and unbelieving--advice, acting with complete freedom and independence with regard to men, but in complete obedience to his Father" (Barrett, John, 313).

"That Jesus eventually goes to the festival ἐν κρυπτῷ is to be interepreted strictly in relation to [John 7:4]: he journeys quietly to Jerusalem, without making any ostentatious entry into the city or drawing attention to himself on arrival at the festival" (G. R. Beasley-Murray, John , 107).