Here Joseph Smith edited justifieth to justifies in the printer’s manuscript, but this change was never implemented in the 1837 or any later edition, perhaps because the following condemneth was not edited to condemns: “behold I say unto you nay but he condemneth you”.
Joseph Smith’s replacement of the -(e)th ending with -(e)s was very unevenly applied in his editing for the 1837 edition. For a complete discussion, as well as a list of examples where he made this change, see under infl al endings in volume 3.
Summary: Retain in Jacob 2:14 the current -eth ending for justifieth, which is the reading of both manuscripts; justifieth is also stylistically consistent with the following condemneth.