Chapter 3 is the doctrinal heart of Benjamin’s Speech. It’s all about the Atonement. The first thing to recognize is the atoning Savior Himself. The angel assures Benjamin that people will know this Redeemer when he comes. He will look like a man and will dwell in a tabernacle of clay, but he will come with powers beyond anything normally seen: "working mighty miracles, raising the dead, causing the lame to walk, the blind to receive their sight, the deaf to hear, and curing all manner of diseases" (3:5).
Among the Dead Sea Scrolls—and this is discussed in this connection in the book, Isaiah in the Book of Mormon composed and edited by me and Donald Parry—there is a text, 4Q 251, that was unknown until just a few years ago. This Jewish text, written in the 1st Century BC, says: "When the Messiah comes, he will heal the sick, make the blind see, raise [or resurrect] the dead, and to the poor announce glad tidings." And another fragment (4Q 541) from that same cave reads as follows: "They will utter many words against him and an abundance of lies." So this was an expectation among some Jews, and here you have the Nephites also knowing this around 124 BC. So that we might recognize the power of the coming Lord, a number of things are given to let people identify this person. When Jesus came working all of these miracles, it’s not just that he was doing amazing things, but he does them so that people will know and identify who has come. Of course, the people of the Book of Mormon will also have some of these things happen in their presence, when Jesus appears after the resurrection and says, "Have ye any that are lame, or blind, or halt, or maimed, or leprous, or that are withered, or that are deaf, or that are afflicted in any manner? Bring them hither and I will heal them" (3 Nephi 17:7). He has raised himself from the dead, and others will be raised from the dead. So all of these signs which Benjamin told the people will be a confirmation to them in their land, as well as to all people, that they might be convinced that Jesus was the Christ, the Eternal God, and how to embrace His Atonement.
Book of Mormon Central, "Why Did Christ Perform Miracles? (Mosiah 3:5)," KnoWhy 508 (March 28, 2019).