Well, I wanted the 23rd Psalm, because everyone's familiar with it. And I had to google for Ezekiel 23; I didn't know where it was, just the verse about "whose genitals were like those of donkeys and whose emission was like that of horses." (It's a favorite among the anti-biblethumper crowd.) So when they were both 23's, I figured I had to find two more 23's to fill in the gaps.