A personage of spirit and the third member of the godhead. The Book of Mormon testifies of the unity of the Godhead in doctrine, purpose, and witness , as well as clearly teaching that the Holy Ghost is a separate and distinct being from the Father and the Son. When Nephi1 described the baptism of Jesus he spoke of each member of the Godhead—the Father, the Son, and the Holy Ghost—as separate and distinct personages.
The Book of Mormon also verifies that the Holy Ghost functioned in Old Testament times. It contains more than 85 direct references to the Holy Ghost, beginning as early as 592 B.C. , when Nephi taught that the Holy Ghost was “the gift of God unto all those who diligently seek him, as well in times of old as in the time that he should manifest himself unto the children of men”. The Book of Mormon restores the knowledge that the gospel of Jesus Christ, including the gift of the Holy Ghost, was received and enjoyed anciently, before the advent of Jesus Christ.
The Book of Mormon identifies various roles of the Holy Ghost. These include bearing witness of the Father and the Son and of all truth, revealing the things of God, bringing spiritual rebirth and sanctification, and administering the gifts of the Spirit.