In the original text, the Book of Mormon often uses the historical present tense in a narrative. In this first example, the narrative starts out in the past tense (“the Lord spake”) but then switches to the present tense (“and saith unto him”). This pattern mirrors the style of the King James Bible in the New Testament (where the distinction is based on the original Greek), as in the following example:
For the 1837 edition, Joseph Smith changed most examples of the historical present to the simple past, as here in 1 Nephi 2:1. Nearly all the cases involve saith, but there are a few other verbs as well. See the discussion under historical present in volume 3.
The word saith is often spelled sayeth in the manuscripts and in the 1830 edition (as here in 1 Nephi 2:1). This spelling supports the idea that Joseph Smith pronounced saith as say +eth /sei.ßh/ rather than as seth /seh/. We follow the standard spelling saith in the critical text since for modern readers it too is typically pronounced /sei.ßh/ rather than /seh/. In other words, every time saith is found in the text, it should be assumed that it is pronounced /sei.ßh/. For a complete analysis, see saith in volume 3.
Summary: Restore the historical present tense whenever the earliest textual sources support it.