Tabernacles (v.2) — celebration of harvest, in the month of Tishri (our mid-September to mid-October). In Leviticus 23, Tabernacles is listed with the feasts of Jehovah. Now it is just called a feast of the Jews. The true meaning of it had been lost, so the Lord didn’t associate His name with it.
Brethren (v.3) — blood relations, probably sons of Mary and Joseph after Jesus was born (Matthew 13:55). At this time, they did not believe Jesus was the Messiah, but by Acts 1:14, they did.
They urged Him, perhaps sarcastically, to show Himself (v.3).
His brothers said “No one who wants to be known acts in secret” (v.4). Were they challenging Him to prove Himself?
Jesus knew the Jews sought to kill Him, so He didn’t go up, not out of fear but because it wasn’t time for Him to die (v.6).
The world did not hate them (v.7) because they were still of the world.
From here on in John, Jesus is seen as the suffering Messiah. Here He suffers the unbelief of His own brothers.