The 1892 RLDS edition omitted the definite article the in the phrase “all the things”. This shortened reading has been followed in all subsequent RLDS editions. Elsewhere in the text there are 22 occurrences of “all things which”—that is, cases where all things is postmodified by a relative clause headed by which. On the other hand, the earliest text has 9 additional occurrences of “all the things which”. In general, either reading will work. The critical text will in each of these cases follow the earliest textual sources in determining the correct reading for the phrase “all (the) things”.
Summary: Maintain in Mosiah 4:9 the definite article in the phrase “all the things” since this is the reading of the earliest textual sources for this passage.