To underscore the current importance of this sermon, Jacob performs a visual action that they could all observe. When he took off an article of clothing to shake them before the congregation, he was symbolically enacting Isaiah 52:2, which was included with Jacob’s quotation of Isaiah 51 (in 2 Nephi 8:25): “Shake thyself from the dust; arise, and sit down, O Jerusalem: loose thyself from the bands of thy neck, O captive daughter of Zion.” Jacob enacts that shaking of the dust before them. He declares that he has done so, visually enjoining them to do the same. At the same time, because they share the same city, shaking off their dust also visually symbolizes his separation from their sins.
Jacob entreats his audience to repent and “turn away from your sins,” to “shake off the chains of him that would bind you fast.” The final exclamation that “I know my guilt; I transgressed they law,” is not Jacob speaking of himself, but his rhetorical quoting of what his audience must say at that great judgment day.