In Luke 1:76-77, we read the following prediction of the mission of John the Baptist:
And thou, child,
shalt be called the prophet of the Highest: for thou shalt go before the face
of the Lord to prepare his ways; to give knowledge of salvation unto his people
by the remission of sins.
In the JST, v. 77 (v. 76 in the JST) reads
differently, informing us of the instrumental means of this “remission of sins.”
The following comes from New Testament Manuscript 2, Folio 3:
to give knowledge of
salvation unto his people, by baptism for the remission of their sins
This change by Joseph Smith explicitly teaches baptismal regeneration. For more on Joseph Smith's teachings where he affirmed this doctrine, see "Appendix 1: Did Joseph Smith Reject Baptismal Regeneration?" pp. 177-192 of my book "Born of Water and of the Spirit": The Biblical Evidence for Baptismal Regeneration (a book which also shows the overwhelming biblical-exegetical evidence for this doctrine). For those who want a free PDF copy, drop me an email at ScripturalMormonismATGmailDOTcom.