"And Saul, yet breathing out threatenings and slaughter against the disciples of the Lord, went unto the high priest,
And desired of him letters to Damascus to the synagogues, that if he found any of this way, whether they were men or women, he might bring them bound unto Jerusalem.
And as he journeyed, he came near Damascus: and suddenly there shined round about him a light from heaven:
And he fell to the earth, and heard a voice saying unto him, Saul, Saul, why persecutest thou me?
And he said, Who art thou, Lord? And the Lord said, I am Jesus whom thou persecutest: [it is] hard for thee to kick against the pricks."
"Prick" in this case, refers not to the kind of person who won't give up the seats nearest the door on BART even when elderly riders clearly need them but to what the OED defines as "A goad for driving cattle, esp. oxen" or, following that, "A thing which serves as a stimulus, prompt, or incitement; a spur, an incentive." Pricks are the pointy parts of the harness that makes it difficult for the animal to move outside of its intended path, to shirk its duty. The phrase "to kick against the pricks" (which can be found in Johnny Cash's song, "The Man Comes Around") has come to mean resistance, but the manner and means of resistance never becomes entirely clear. For example, the OED provides this in-context example from 1904: "For the past ten years he has known what it is to ‘kick against the pricks’ of legitimate Church authority." The connotation of "kicking against the pricks could be two-fold. In this case, if "legitimate Church authority" is unjust, then resisting it would be a noble act of rebellion. However, if the Church is pursuing legitimate goals and acting justly then the rebel only increases his own misery an delays his proper path, like Jonah. Like most things, the phrase seems conditional, dependent on objective and subjective context.
What did Jesus mean in this case? He defines who he is by Saul's actions: "I am Jesus whom thou persecutest." Then, directly connected to that thought, he deploys that tricky metaphor. Since the story of Saul's conversion into Paul is itself often used as a metaphor for righteous duty, interpreting Jesus' metaphor outside of this framework becomes problematic, especially for those raised in an evangelical environment. Sometimes it takes a friend to point out other possibilities. What if the honorable thing for Saul to do was simply stop persecuting Christians? In that case, is his work as an apostle a story of blind obedience and submission or truly a radical conversion?