According to John Welch, unlike the Sermon on the Mount, the Sermon at the Temple mentions no penalty concerning the unchaste eye that should be cast out if it offends (see Matthew 5:29). This has been a troublesome point for many biblical commentators, for Jewish attitudes around the time of Jesus were strongly set against any punishment that took the form of bodily mutilation… All references to plucking out the eye or to cutting off the hand that offends are absent in the Book of Mormon text, suggesting that this problematic verse in the Sermon on the Mount, on its face, does not fully reflect Jesus’ original intent. Instead, the Sermon at the Temple speaks at this point of a total commitment -- of the disciple taking up a symbolic cross (3 Nephi 12:30), a symbol of capital punishment… . The image this may bring to mind is that of a covenanter taking this obligation very seriously, for hanging or exposing a body on a tree or on a cross was part of the standard punishment under the law of Moses for any person who committed a sin worthy of death. [John W. Welch, The Sermon at the Temple and the Sermon on the Mount, F.A.R.M.S., p. 52]
3 Nephi 12:30 Take up your cross ([Illustration] Ancient American Crosses. (Above) This carving from lintel 2 at Yaxchilan shows that crosses had ceremonial significance to the ancient Americans. Many archaeologists call the crosses (left & right) the Tree of Life. From what we know of the Book of Mormon that makes little difference. The hand-held crosses (above) are obviously not trees. (Below) The top of this tomb in Oaxaca has been removed demonstrating another of the many uses of the cross in ancient America. [Glenn A. Scott, Voices from the Dust, p. 210]