Mosiah 18:2

yea, concerning that which was to come, and also concerning the resurrection of the dead, and the redemption of the people, which was to be brought to pass through the power, and sufferings, and death of Christ, and his resurrection and ascension into Heaven.

He taught about what would happen. He taught about people rising from the dead. He taught about how Jesus would save people. He taught about Jesus’ power, suffering, and death. He taught about Jesus coming back to life and going to heaven.

He spoke about what was coming—the day when the dead would rise, when God’s people would be set free through the power, suffering, and death of Christ, and through his rising from death and return to heaven.