Textual: At this juncture, two verses are completely excised from the Matthean account and replaced completely in 3 Nephi. The Matthean verses present at this same location are:
Matthew 5:29-30
29 And if thy right eye offend thee, pluck it out, and cast it from thee: for it is profitable for thee that one of thy members should perish, and not that thy whole body should be cast into hell.
30 And if thy right hand offend thee, cut it off, and cast it from thee: for it is profitable for thee that one of thy members should perish, and not that thy whole body should be cast into hell.
The replacement of these verses is interesting, as they are clearly problematic in their metaphorical instruction to pluck out eyes and cut off hands. Rather than repeat the difficult phrasing, Joseph translates meaning as the Sermon appears in 3 Nephi. When the similar location is addressed in the Joseph Smith Translation of the Bible, the solution is slightly different in that the Book of Mormon additions are retained in addition to the Matthean text:
“Behold, I give unto you a commandment, that ye suffer none of these things to enter into your heart, for it is better that ye should deny yourselves of these things, wherein ye will take up your cross, than that ye should be cast into hell.
Therefore, if thy right eye offend thee, pluck it out and cast it from thee; for it is profitable for thee that one of thy members should perish, and not that thy whole body should be cast into hell.
Or if thy right hand offend thee, cut it off and cast it from thee; for it is profitable for thee that one of thy members should perish, and not that thy whole body should be cast into hell.
And now this I speak, a parable concerning your sins; wherefore, cast them from you, that you may not be hewn down and cast into the fire. (JST; italics added.)” (Daniel H. Ludlow, A Companion to Your Study of the New Testament: the Four Gospels. Salt Lake City: Deseret Book Co., 1978, p. 53)
The JST retains the more difficult text, but attempts to make its import clearer through the additional text. The 3 Nephi solution is to simply replace it.
Of course the ultimate meaning of both the Matthean and the 3 Nephi passages is to require us to root out the evils that might damage our soul. Sometimes those things may appear to be important to us, or they may be physical addictions. Many a convert to the church understands the difficulty with which certain physical addictions had to be rooted out of their body and heart. That is the impact of these verses. The harm to our souls comes from long-term harboring of these feelings that may escalate to more damaging feelings or actions. We are to remove them. The Matthean metaphor is cutting off an important part of the body. The 3 Nephi example is taking up the cross, a symbol of the purification of sins through the atonement.