Here in the original manuscript, it is difficult to tell whether Oliver Cowdery wrote whither or whether. As discussed under 1 Nephi 22:4, in each case of whither /whether the context will determine which reading should be accepted. We cannot rely on Oliver’s manuscript spellings of whither /whether since he tended to mix them up. Here in Alma 48:16, whether is definitely incorrect since the larger passage makes it clear that Moroni intends to defend the Nephites and lead them into battle against the Lamanites: “and he had sworn with an oath to defend his people / his rights and his country and his religion / even to the loss of his blood” (Alma 48:13). The question in verse 16 is where the Nephites should go to defend themselves. For other examples of whither referring to where the Nephites should go, see under Alma 16:5 and Alma 43:22–23.
Summary: Retain in Alma 48:16 the correct whither (rather than whether) since the question here is knowing where the Lamanites will attack.