Since Cumorah, Nibley, pp. 7, 151; Companion to Your Study of the Book of Mormon, Ludlow, p. 120
“This clause first appeared in the 1840 and 1842 editions of the Book of Mormon. It did not appear again until the 1920 edition, and it has been in all editions since that time. It appears to be a prophetic commentary by Joseph Smith to explain the meaning of the phrase ‘out of the waters of Judah.’ … If this phrase were a restoration of the original text, as found in the more pure version on the brass plates from which it comes, it would have appeared in the 1830 edition of the Book of Mormon… . Through the use of this phrase, Joseph Smith is calling our attention to the fact that the ordinance of baptism was as common to the people of the Old Testament as it was to the people of the Book of Mormon.” (R. Millet and J. F. McConkie, Doctrinal Commentary of the Book of Mormon, 1:151-152)