In his editing for the 1837 edition, Joseph Smith removed this example of “saith the prophet” since it had already occurred in the same sentence. Such redundancies are often editorially removed from the text, even though the original repetition is not particularly bothersome. In fact, throughout this portion of the text, the phrase “saith the prophet” is found in almost every verse (six times from verses 12 through 17), although it is never otherwise repeated within the same sentence. The critical text will, of course, maintain such redundancies.
Summary: Restore the repeated “saith the prophet” in 1 Nephi 19:13 since it appears to be intentional.