This verse describes the Millennium after the wicked are destroyed by fire (2 Nephi 30:10), or the glory that attends his coming (see D&C 101:23–25). The pronoun “his” represents Christ. The “girdle” is his clothing, symbolic of his character. He is clothed with righteous actions. His “reins” represent his feelings of pure love or perfect love (see Moroni 7:48 and 1 John 4:16–19).