This is a wonderful little aside in the story of the Gospel. Peter declares here that the Gospel story has been the subject of revelation in the Old Testament. This is exactly what everything in God’s Word had been hinting at and revealing.
A lot of people like to treat the Gospel as the stuff for beginners, when it comes to faith and theology. They like to point out that they have surpassed that “baby’s milk” of spiritual truth and they have moved on to “deeper” truth. They are more mature. Be it any number of secret truths that only the wise can grasp: Holy Spirit stuff, secrets to successful living, power, etc.
The truth is that it does not get any deeper than the Gospel. The story of the incarnation, sacrifice, and resurrection of the Christ and all that that implies is so deep we will spend an eternity failing to fully grasp it all. This is the stuff that prophets searched and angels long to see clearly.
If you have fallen into the trap of thinking the salvation story is minor, beginner’s fare; if you are unmoved by the beautiful truth revealed on the cross; then you need to look again. Reexamine the story. The grace of God is the most amazing realization you will ever experience, and when you do begin to see the vastness of that truth, you will never tire of it. It will impact every aspect of your life.