The original manuscript here reads preserve, which Oliver Cowdery misread as reserve when he copied from 𝓞 into 𝓟. The 1981 LDS edition restored the correct preserve in the LDS text. As discussed under Alma 17:31, either reading will actually work here since in Early Modern English the word reserve had the meaning ‘preserve’. Here in Alma 37:18, we follow the earliest textual source (namely, the original manuscript) and maintain preserve. Usage elsewhere in this chapter supports the use of preserve in referring to the promise the Lord made that he would not allow these records to be lost:
The same language is also found in the Lord’s original promise to Nephi, as recorded in the small plates of Nephi:
Summary: Maintain in Alma 37:18 the original verb preserve rather than the misreading reserve that Oliver Cowdery introduced into the text when he copied from 𝓞 into P.