The immense faith of the brother of Jared gave him the privilege of parting the veil and seeing the spirit body of the Savior. “Because of thy faith thou hast seen that I shall take upon me flesh and blood” (emphasis added). The brother of Jared was seeing what Jehovah would look like when he came into the world as Jesus Christ. The Savior’s spirit body resembled the body he would inhabit centuries later in mortality (see also D&C 77:2).
The prophet’s faith was so perfect that his redemption was secured—that is, his calling and election was made sure—and, even as a mortal, he was “brought back into my presence; therefore I show myself unto you” (see also commentary at Alma 36:28).