Jeff Lindsay notes that scholars have found that Book of Mormon passages apparently from the King James Version of the Bible contain variants corroborated in other biblical texts. John Welch discusses one example:
The Sermon at the Temple begins 3 Nephi 13:1 with a sentence that is not present in the Sermon on the Mount: "Verily, verily, I say that I would that ye should do alms unto the poor" (3 Nephi 13:1). Since this text makes the topic of these verses explicitly clear, continuing with a reference to "righteousness" would have been awkward, although this could have been done and the reader still would have understood its meaning to be "righteous almsgiving."
Moreover, in Hebrew (and presumably in the Nephite language) there is not nearly so much difference between the two Semitic words "righteousness" (zedeq) and "almsgiving" (Syriac, zedqtha; Hebrew zodaqah, which at Qumran meant "righteousness . . . justified by charity"), as there is between the two Greek words dikaiosune ("righteousness") and eleemosune ("generosity"). Indeed, one of the most important attributes of any person (including God) who is zedeq is that he is charitable: he "gives freely, without regard for gain." "The righteous (zedeq) hath mercy and giveth" (Psalm 37:21; see also Daniel 4:27 [Hebrew text 4:24]). If Jesus said in Hebrew, "Watch your zedeq," What did he mean? His message was about generosity, not just "righteousness" in some general sense. The Greek word dikaiosune (from dike, "justice") is, therefore, not a satisfactory term to convey the full meaning of the Hebrew zedeq or its Aramaic cognate, the languages Jesus spoke. "Doing alms," on the other hand, comes closer to conveying the meaning of "righteousness justified by charity." Assuming that Jesus said to the Nephites something like, "Watch your zodaqah" (since he would not have spoken to the Nephites in Greek), Joseph Smith was most correct to translate this by reference to charitable "alms." (John W. Welch, The Sermon at the Temple and the Sermon on the Mount, p. 150)
[Quoted by Jeff Lindsay, "Did Joseph Smith Plagiarize from the King James Bible?," Book of Mormon Commentary, [www.jefflindsay.com]]