This verse may be a paraphrase of 3 Nephi 27:20: “Now this is the commandment: Repent, all ye ends of the earth, and come unto me and be baptized in my name, that ye may be sanctified by the reception of the Holy Ghost, that ye may stand spotless before me at the last day.”
Mormon has indicated that the faith of some may be established on the direct experience of others. For Mormon, the best example of such experience is the Messiah’s appearance at Bountiful. For Mormon it was a solid reality upon which to build firm faith. Because it happened, we may understand (and therefore have faith) that God’s other promises will be fulfilled.