The Holy Ghost is part of the godhead in which we believe.
Sent by the Father in Christ's name.
Sent by Christ from the Father.
"Spirit of Truth"
Shall testify of Christ.
Will show things to come.
Will guide in all truth.
Will glorify Christ.
Would not come (as Gift) until after Christ's Death.
While seeking the brass plates, Nephi is guided by the spirit and commanded to kill Laban.
Jesus was to send the Holy Ghost from the Father and he was to testify of Jesus.
Jesus had to leave before the Holy Ghost could be sent.
Simon is blessed because he has received a witness of Christ's divinity from God. (Through the Holy Ghost.)
Gospel preached in the beginning (in the days of Adam) by the gift of the Holy Ghost.
The Gift of the Holy Ghost is manifest on the Day of Pentecost.
As cited above in John 16:7, Jesus had to leave before the Holy Ghost could be sent. This is generally understood to be a reference to the Gift of the Holy Ghost, as there is scriptural evidence for the power of the Holy Ghost being in operation during the life of Christ. (See: Matthew 16:17) However, scriptural evidence also indicates that the Gift of the Holy Ghost was operating way back in the days of Adam. (See: Moses 5:58)
So the evidence suggests that the Gift of the Holy Ghost has always been present in the various dispensations, except that it was absent during the life of Christ for some reason. After he left, the gift of the Holy Ghost returned, as evidenced on the Day of Pentecost (See: https://www.lds.org/scriptures/nt/acts/2?lang=eng#0) and on future occasions as the power of the Holy Ghost was especially manifest following baptism and confirmation.
This begs the question, why was the Holy Ghost absent during Christ's life?
Some thoughts that cross my mind:
- Perhaps withholding the Gift of the Holy Ghost emphasized the nature of the authority that Christ had on his own.
- Perhaps the Gift of the Holy Ghost was not needed as an authoritative figure. Presumably, since the Holy Ghost is a member of the Godhead, he has some kind of authority, perhaps even delegated keys. The Gift of the Holy Ghost could then be seen as providing the constant companionship of the spirit in the sense that the Holy Ghost resides with us and authorizes us to act as God's agents in utilizing the power of the Holy Ghost, whereas, when Christ was on the Earth, he personally directed the utilization of God's power, or the power of the Holy Ghost as it were, as well as the priesthood power, and the Holy Ghost may not have been needed in person.
Whatever the true reasons for this absence, it might serve to illustrate the distinction between the power of the Holy Ghost and the Gift of the Holy Ghost, by the dramatic difference in the Holy Ghost's manifestations after the Day of Pentecost.
Further question: Was the gift of the Holy Ghost only absent in the old world, or was it absent also in the New World. (A review of 3rd Nephi should be suggestive.)