There were things that were kept a mystery from the beginning of creation, until the last days before Christ's return. Peter refers to one of these mysteries in verse 4-5. "Who are kept by the power of God through faith for salvation ready to be revealed in the last time."
Before Christ, the only communication between God and the individual was based on animal sacrifices as a picture of the holiness of God and of our need for forgiveness. But Jesus came with the new message and the end of animal sacrifice. "The Spirit of Truth... you know Him, for he dwells with you and will be in you" (John 14:17).
We understand more about salvation than the people in the Old Testament knew, but we shall understand even more when we reach heaven (1John 3:1-3).
