The path of the righteous man is beset on all sides by the inequities of the selfish and the tyranny of evil men. Blessed is he who, in the name of charity and good will, shepherds the weak through the valley of darkness, for he is truly his brother's keeper and the finder of lost children. And I will strike down upon thee with great vengeance and furious anger those who attempt to poison and destroy my brothers. And you will know my name is the Lord when I lay my vengeance upon you.
There's Jules' favorite Bible passage in all its glory.
Jules takes some poetic license with the passage, though, probably to amp up the effect. Here's Ezekiel 25:17 from the NIV Bible: "I will carry out great vengeance on them and punish them in my wrath. Then they will know that I am the LORD, when I take vengeance on them." That Old Testament God can be as scary as Jules sometimes, eh?
Many sources attribute this faux verse to Tarantino, assuming he invented it as part of the script. But those people have never seen the 1976 English version of the 1973 Japanese martial arts movie Karate Kiba, a.k.a., Chiba the Bodyguard, starring everybody's favorite mid-'70s martial arts hero, Sonny Chiba. Wait, you've never heard of it either? Well, lucky for you that Tarantino is the ultimate movie fan (watching them, not just making them), so he wrote the intro of Chiba the Bodyguard into Pulp Fiction with just a slight variation. Check it out for yourself here.
We're not kidding—that's the real introduction to the movie.
Jules himself gives us a few different interpretations of why he uses this passage. At first he says it was "just a coldblooded thing to say" to someone before he shot them. Since the miracle, he's been asking himself: Who is the righteous shepherd? And who is the tyranny of evil?
Now, Jules would love to be the shepherd, but he knows he's not shepherd (probably because he kills people for a living), and he's certainly not the weak since he's the one with the gun. He has control of the situation with Ringo in the diner and with Brett and the boys. That makes Jules, as much as he hates it, the tyranny of evil.
This realization causes him to give up his life as a gangster and try to become a shepherd; and what better place to start than shepherding the man right across the table from him. Ringo makes it out with $1500+, his life, and a nice little lesson.