Can you clear up the alleged contradiction between the passages in which Jesus said He would not drink the fruit of the vine until the kingdom and the tasting of sour wine on the cross?

Briefly, when Jesus speaks in Matthew 26:26; Mark 14:25; and Luke 22:18 He is, in each case, observing Passover with His disciples. Here, He is not just drinking a cup of wine, He is participating in the fellowship of God's table, which is a prototype of the fellowship meal we will have in heaven (see Psalm 23:5; compare Exodus 24:9-11; Luke 12:37). Jesus is not speaking technically, as to when wine will next touch His lips; He is speaking figuratively of the future celebration of the great supper in heaven.

The passages in the gospels which speak of the sour wine that was offered to Jesus really have almost nothing in common with the texts above. It is not a meal that is offered, or even a cup of wine -- it is a kind of pain reliever that is offered (Proverbs 31:6). Notice that our Lord declines the first offer, at the outset of His ordeal on the cross (Matthew 27:33-34), because He purposed to "drink the cup of suffering to the full."

But He did accept the last offer of sour wine. This was just moments before He uttered His final words, "It is finished" (John 19:29-30). There was no time for the wine to take effect. This, in my opinion, was more like mouthwash that allowed our Lord to clear His throat and to speak His final words clearly.