Ross Geddes has suggested (personal communication, 18 September 2005) that the reading “the people of that church” here in Mosiah 26:33 is an error for “the people of the church”. The nearest preceding reference to the church is some distance away, in verse 21, so the use of that church here in verse 33 is unexpected. Geddes also points out that elsewhere in this chapter there are 13 references to the church, but none to that church. However, it should be pointed out that the Lord refers to Alma as having established “a church” (in verse 17), which the Lord later refers to as “my church” (in verses 22 and 28). These additional examples with a and my suggest that other churches are conceptually possible. Yet there is only one church actually referred to in the entire book of Mosiah, the church of God established by Alma. In other words, there is no other specific church mentioned that could serve as a contrast to Alma’s church. Thus the reference to that church seems inappropriate. In fact, the Book of Mormon otherwise has no examples of that church except for ten instances of “that great (and abominable) church”. Clearly, the use of that church is odd here in Mosiah 26:33.
Geddes proposes that the that accidentally entered the text in Mosiah 26:33 because of two preceding occurrences of the subordinate conjunction that (“he wrote them down that he might have them that he might judge the people of that church”). There is some manuscript evidence that the was sometimes replaced with that (although there are many more examples in the manuscripts of the opposite tendency, to replace that with the). We do have two cases where Oliver Cowdery initially wrote that instead of the; in both cases he soon corrected the that to the (there is no change in the level of ink flow):
Both of these examples involve city, not church. The text has 11 examples of that city; there are also 10 examples of that great city, nearly all of which are followed by the name of a city. Thus Oliver’s two initial errors involving that city were quite natural. But there is no other evidence for that church in the text beyond its specific use in “that great (and abominable) church”.
Since the manuscript evidence for replacing the with that is relatively meager and that church is not impossible (although exceptional), the critical text will maintain that church, the reading of all the (extant) textual sources for this passage. But there remains a good chance that the unique occurrence of that church here in Mosiah 26:33 is an error for the church.
Summary: Retain the unique reading that church in Mosiah 26:33; this reading could well be an error for the church.