Now it was told Saul that David had come to Keilah. And Saul said, “God has given him into my hand, for he has shut himself in by entering a town that has gates and bars.” And Saul summoned all the people to war, to go down to Keilah, to besiege David and his men. David knew that Saul was plotting harm against him. And he said to Abiathar the priest, “Bring the ephod here.” Then David said, “O Lord, the God of Israel, your servant has surely heard that Saul seeks to come to Keilah, to destroy the city on my account. Will the men of Keilah surrender me into his hand? Will Saul come down, as your servant has heard? O Lord, the God of Israel, please tell your servant.” And the Lord said, “He will come down.” Then David said, “Will the men of Keilah surrender me and my men into the hand of Saul?” And the Lord said, “They will surrender you.” Then David and his men, who were about six hundred, arose and departed from Keilah, and they went wherever they could go. When Saul was told that David had escaped from Keilah, he gave up the expedition. (1 Samuel 23:7-13)
It's easy to get fascinated by the conditional foreknowledge of God in this passage. God tells David what will happen if he chooses a certain path, David decides to not go down that particular path, and the foreseen event does not take place. This is the stuff science fiction alternate timelines are made of. This is the basis for the multiverse, a philosophical theory which tries to disprove God by building an infinite number of possibilities for existence to happen naturally.
But, we can't miss the prophecy in this passage (which I ignored this past Sunday) that this Godly prediction of what MAY happen to David, and did not, actually DID happen. This is a prophecy of Christ.
The devil was quite pleased at the incarnation. The father had made the drastic "mistake" of giving his son into the enemy's hand. What foolish action could be worse than the incarnation? In the parable of the wicked tenants, they laugh as they say to themselves, "here comes his son! Now the inheritance will be ours when we kill him!" Christ was made vulnerable, emptied into the form of a mere man, who could be killed. On earth there is no place to hide, and so it was only a matter of time for Satan to be satisfied in his conquest of the Lord's life.
Furthermore, Jesus knew all of this. He knew that he was to be killed, but he knew that his death would a victory over the devil, not a loss. Whereas David left Keilah, in order to avoid his fate, Jesus remained, and he even walked into the danger, knowing that it must happen for the salvation of the world. The devil wants the destruction of the whole church on Christ's account, and what David asked the Lord came true: the world turned Jesus over to the devil in order to save itself. We crucified Christ. Jesus also told us that after he was gone, the world was going to continue to persecute the church on his account. Read the newspapers and see that this prophecy, too, has come to pass. We surrendered our savior into the hands of evil men, and as a result, the evil men continue to persecute us for his sake.
So, when David asks the Lord if Saul will come down, the Lord does not lie. The spirit of Saul, the false church, does come down. And the men of Keilah, the city that David saved from destruction in the previous passage, does surrender the savior over to evil men. The church is saved from destruction by the very act of turning the savior over to evil men. The very idea that our wickedness toward Christ becomes the very act that sets up eternal salvation for believers testifies to the truth of scripture. The stone that the builders rejected has become the chief cornerstone. Repent and believe the gospel.