Question:

The Gospel authors weave OT passages and themes into their various portraits of Christ, e.g., John’s Gospel fabricated a narrative that depicts Jesus being offered sour wine to fulfill the second half of Psalms 69:21, but that lacks anyone trying to poison Jesus to fulfill the first half of this passage. In reality, there is nothing predictive about this passage, and so neither Jesus nor the guards had to act the way they did. Similarly, Psalms 22 is not about Jesus at all. Mark was familiar with the Psalms and deliberately fabricated stories about the mocking of the crowds and the distribution of his clothes.  What is your answer?

Answer:

The reason that the gospel writers mention Jesus being offered sour wine is that he was offered sour wine to drink.  There is no reason for the authors, Matthew, Mark and John, to fabricate such an event, given that those who were there at the time could either confirm of disconfirm the statement.  Similarly, the gospel writers record of Jesus that “they pierce my hands and my feet.” because they did in fact pierce his hands and feet.  One can question the validity of the offer of sour wine, as this is the testimony of a relatively few people, but there is no doubt whatsoever that Jesus was crucified!!!  So, these passages record what happened to Jesus because this is what happened to Jesus.  This is the most reasonable conclusion.
Let me be honest here.  If the only messianic prophecy mentioned in the New Testament was Psalm 69:21, I would say that this would be a somewhat weak example, and weak proof that Jesus was the prophesied Messiah.  I believe that the event with the sour wine happened, but the witness testimony is perhaps a bit weak. And I believe that Psalm 69:21 is a prophecy of this event, but it is not a crazy idea to think that this was not being prophesied by Psalm 69:21–that it is taken out of context by John.  However, with the other case you cite, the situation is much different, as can be said of many other messianic prophecies. The case for the fulfillment of messianic prophecies is based on a cumulative study of all the prophecies.  One of the strongest ones is Psalm 22:15-19, in which David describes being surrounded by enemies, having his hands and feet pierced, his garments being both divided and gambled over, and his bones, surprisingly not being broken.  All of these are things that, as far as we know, never happened to David, but we know that they happened to Jesus when he was crucified.  His crucifixion is a matter of historical fact.
Mark did not “weave” the idea of the crucifixion into his description of the death of Jesus. This claim is ludicrous.  And that this is prophesied in Psalm 22:16, to me, speaks for itself, although some might disagree.  There is no evidence that Mark fabricated the stories of Jesus being mocked, or that John (and Mark by the way) fabricated the event of the sour wine.  We KNOW he did not fabricate the means of death.  Why would he accurately record true prophecy fulfillments, and then fabricate others?  Mark believed Jesus was the Messiah.  It makes no sense that he would tell lies in order to get people to believe in something for which there was a vast amount of evidence.  This claim simply makes no sense.
Then we come to the second question, which is whether the gospel writers take a statement in the Old Testament and tweek it to be a prophecy of what happened to Jesus, or whether these are in fact historical messianic prophecies.  And given the many eye-witnesses to the actual events, for Mark to invent lies would have been a really bad idea, as it would have undermined everything he said.  No! Mark recorded these things because they happened.  Psalm 69:21 is relatively weak as “proof” of Jesus being the Messiah, but Psalm 22:16 and MIcah 5:2, Zechariah 9:9, Zechariah 11:12-13 and Isaiah 53 (the whole chapter) are wonderfully strong evidence, from which the cumulative case of Jesus being the Messiah, prophesied in the Old Testament is a slam dunk.
John Oakes