Why is it correct to say "it later came to pass" instead of "it came to pass later"? What is the rule for this placement?
Neither is necessarily incorrect; I also can't imagine that one is necessarily worse, at least without knowing the context.
The semantic distinction between the two (putting aside the different poetic properties that StoneyB mentions) is a subtle one of emphasis.
- It later came to pass... This phrase is somewhat of an idiom in English, a familiar phrase. It recalls a story-telling tone, and expresses a segue as from one time period to another.
- It came to pass later... Here the later does (granted) feel a bit out of place, and as such the phrase seems to emphasize the later condition of whatever it is, rather than it itself.