For the 1837 edition, Joseph Smith changed yieldeth to yields. However, he did not change the subsequent three verbs that retain their original -(e)th ending (putteth and two occurrences of becometh). This kind of editing has often been inconsistently applied to the text; in this instance the original parallelism in the inflectional ending has been partially obscured. The critical text will restore all cases of the biblically styled -(e)th ending whenever they are supported by the earliest textual sources. For a complete discussion, see under infl al endings in volume 3.
Summary: Restore in Mosiah 3:19 the original yieldeth, which makes this sentence fully consistent in having the inflectional -(e)th ending for each of its conjoined verbs.