Spirit of Christ . . . in them--(Acts 16:7, in oldest manuscripts, "the Spirit of Jesus"; Revelation 19:10). So JUSTIN MARTYR says, "Jesus was He who appeared and communed with Moses, Abraham, and the other patriarchs." CLEMENT OF ALEXANDRIA calls Him "the Prophet of prophets, and Lord of all the prophetical spirit."
did signify--"did give intimation."
of--Greek, "the sufferers (appointed) unto Christ," or foretold in regard to Christ. "Christ," the anointed Mediator, whose sufferings are the price of our "salvation" ( 1 Peter 1:9, 1 Peter 1:10), and who is the channel of "the grace that should come unto you."
the glory--Greek, "glories," namely, of His resurrection, of His ascension, of His judgment and coming kingdom, the necessary consequence of the sufferings.
that should follow--Greek, "after these (sufferings)," 1 Peter 3:18-22 , 5:1 . Since "the Spirit of Christ" is the Spirit of God, Christ is God. It is only because the Son of God was to become our Christ that He manifested Himself and the Father through Him in the Old Testament, and by the Holy Spirit, eternally proceeding from the Father and Himself, spake in the prophets."
Excerpt taken from the Jamieson-Fausset-Brown commentary on 1 Peter