I'm not sure O'Connor based her novel around biblical allusions so much as a parody of the blinding of Saul, or St. Paul (Acts 8 & 9). More importantly, the novel lovingly parodies Thomism, Calvinism, and existentialism to form a pastiche that, as a whole, functions as a polemic against watered-down "civil religion."
As novelist Walker Percy says in The Last Gentleman (1999), "Do you think it is possible to come to Christ through ordinary dislike before discovering the love of Christ? Can dislike be a sign?" It was so for St. Paul, on whose blinding Miss O'Connor bases Hazel's. Paul too was a zealous persecutor of Christians before becoming its greatest proselytizer. The antithesis of love in such matters is not hate, but indifference. Hazel is not indifferent, or ultimately a Nihilist; he exiles himself in a mock-hatred which is but a soured variation of the very love he professes to hate in order to protect himself against indifference. He is a Christian, like Saul, in denial of his salvation because he has been cut off from Christ in a physical world that has not been reconciled with the spiritual.
O'Connor also grotesquely parodies the Virgin Mary (in Sabath Lilly), the holy spirt (in the wise blood of Enoch Emory), and even Christ (in the "new jesus" mummy Enoch steals from the museum).