One purpose of the Book of Mormon is to establish the Bible’s truth (1 Nephi 13:40). Another is to restore “plain and precious things” which were lost from Bible (1 Nephi 13:24-29). After the Book of Mormon’s publication, God set Joseph Smith another large scriptural task: restore the Bible. The Bible is that important.
Under inspiration from heaven, Joseph restored much that was lost and corrected many errors. We usually call the result the Joseph Smith Translation (JST), though it is not a translation between languages. The LDS Church still uses the King James Version (KJV) – a longer story – but many JST excerpts are in footnotes and an appendix to the LDS publication of the KJV. Several whole chapters are included in the Pearl of Great Price. Noticing these enriches our reading and teaching.
For example, the JST version of the early chapters of Genesis is published in the Pearl of Great Price as the Book of Moses; the expansion is dramatic and priceless.
When Moses shows wonders to Pharaoh, beginning in Exodus 7, the KJV says that God hardened Pharaoh’s heart (Exodus 7:3, 13). The JST has Pharaoh hardening his own heart.
When John records – according to the KJV – both that Jesus baptized (John 3:22) and did not baptize (4:2), the JST says instead, in the latter case, that Jesus performed baptisms, but not as many as his disciples.