At first, Peter doesn’t fully get it. He knows that Jesus is the Christ, the Son of the Living God. He knows Jesus is God in the flesh. He understands the nature of Jesus. But he doesn’t understand the work of Jesus. When our Lord tells Peter that He must suffer and die, Peter can’t see past the initial shock. Peter wants Jesus to build a glorious earthly kingdom of power and might. And when Jesus burns that image to ashes before his eyes, Peter can’t see the greater kingdom behind the smoke.
But in our reading from Acts, the Holy Spirit has fulfilled the promises Christ made to Peter. He’s brought to Peter’s remembrance all that Jesus declared to him, and Peter now sees it clearly. Jesus is the cornerstone rejected by His people, not so that God’s kingdom can be torn down, but so that an eternal kingdom, a kingdom of infinitely greater glory can arise from the rubble.
And it has. Through the word that Peter and the other apostles preached, the Kingdom of Christ grew. It spread throughout Judea, throughout Asia Minor, Asia, into Africa, and Europe, into the hearts of those chosen by God from the foundation of the world. So be at peace. The nature and the work of Jesus Christ are clear. Our Lord is true God and true man. He’s the Son of the Living God, born of Mary, the one who died upon the cross, the one who burst forth from His empty tomb and who has sworn to shatter your grave into a million pieces and lift you up into glory on the Last Day. Jesus Christ, the rejected stone, has become the victorious cornerstone. And underneath the weight of that glorious cornerstone, God has crushed your sins and given you the right to live forever within His kingdom of peace.