John 7 is a story about conflict over Jesus' identity. Jesus' brothers as well as the crowds at Jerusalem believe that Jesus is some sort of great rabbi or wonder-worker, but they do not believe that he is the Messiah. Much of the account depicts Jesus' invitation to move beyond deficient beliefs about him.
The story starts with an interesting dialogue between Jesus and his brothers, who, we are told, do not yet believe in him. The brothers want Jesus to publicly proclaim himself at the Feast of Tabernacles. Jesus responds "My time is not yet here... You go up to this feast. I am not going up to this feast, because my time is not yet fulfilled" (John 7:6-8) But then Jesus goes secretly halfway through the feast.
Some Bibles have "I am not yet going up to this feast." Some ancient manuscripts have "not" (ouk) and others have "not yet" (oupo). It seems more likely that John originally wrote ouk. The earliest manuscripts (p66, p75, B) have this reading. But more importantly, we can imagine a pious scribe changing "not" to "not yet" in order to preserve Jesus' honesty; it is very difficult to imagine a scribe changing "not yet" to "not." (On the other hand, the reliable 4th century ms Sinaiticus has oupo, leading the UBS Committee to give a C rating to their decision in favor of ouk).
So why did Jesus say "I am not going up to (or at) this festival"? John loves to use plays on words (see some of my other posts on John). Elsewhere in John, going up (anabaino) is used to refer to Jesus' "glorification" - his crucifixion, resurrection and ascension (John 3:13, 6:61-62, 20:17). The "hour" is also a reference to Jesus' glorification (John 4:21, 23, 5:25, 28, 7:30, 8:20, 12:23, 27, 13:1). So Jesus may be saying that this festival is not the time for him to display his glory through his death; he must wait for the following Passover. This pattern - Jesus uses a play on words, and someone else misunderstands - can be found in other places in John (3:3-5, 4:9-11).
Although I have read the passage as a subtle reference to Jesus' coming glorification for some time, I recently discovered that some church fathers read it this way. Augustine and Chrysostom seemed to view the passage in this way, and (according to Beasley-Murray, who thinks the view is nonsense) so did Ephraem and Epiphanius. Augustine and Chrysostom were not viewing the passage that way in order to preserve Jesus' honesty, since they were working with manuscripts that said "not yet."
[However, it is possible that there is no play on words here; anabaino is the standard word used for going up to Jerusalem, especially for a festival (John 2:13, 5:1, 7:8, 10, 14; 11:55, 12:20).]
The picture: Jesus teaching in the Temple, Michelangelo, 1548.