Cornerstone, Keystone, Stumbling Block

1 Peter 2:6-8

⁶For it stands in Scripture: “Behold, I am laying in Zion a stone, a cornerstone chosen and precious, and whoever believes in him will not be put to shame.” ⁷So the honor is for you who believe, but for those who do not believe, “The stone that the builders rejected has become the cornerstone,” ⁸and “A stone of stumbling, and a rock of offense.” They stumble because they disobey the word, as they were destined to do.

The imagery of Christ as our Rock was not born in the imagination of Peter. It stems from several Old Testament descriptions of the coming Messiah as a Stone – our firm foundation and Savior. I’m going to lean heavily upon the commentary work of Mark Jeske, for he does an excellent job of expanding these concepts.

Isaiah 28:16

… therefore thus says the Lord God, “Behold, I am the one who has laid as a foundation in Zion, a stone, a tested stone, a precious cornerstone, of a sure foundation: ‘Whoever believes will not be in haste.’

Here in Isaiah, the Messiah is described as the cornerstone.

Today the laying of a cornerstone has a mostly ceremonial purpose. The stone’s face bears the year of construction, and it is often hollowed out to receive a time capsule of treasured objects and papers. The real structural value of the cornerstone, if you are a stone mason, is to serve as the point of reference for the straightness of the building. The cornerstone is the first, and also largest, stone above grade. As such it must be quarried, measured, sawed, shaped, and finally mortared into place with great precision. Masons build a building up from the corners. That first stone will determine the straightness of the building’s lines of depth, width, and height. If the cornerstone is off a little, the whole building will end up looking crooked, because all the stone or brick get their lines from the corner. In the same way, Jesus Christ is the standard of straightness in our lives. In a world full of Satan’s lies and deceptions, the Word of the Lord remains straight and true. His word of law cuts through the excuses, rationalizations, and moral compromises of all ages and cultures and holds us all accountable to God’s unchanging standards. His word of gospel cuts through all Satan’s lies about our own worthlessness and despair and holds before us the unchanging love of the crucified and risen One. Whoever builds his or her life along these true lines will never regret it, neither in one’s earthly life nor on judgment day.

Jeske, M. A. ©2002. James, Peter, John, Jude (p. 88). Milwaukee, WI: Northwestern Pub. House.

Psalm 118:22

The stone that the builders rejected has become the capstone [or keystone].

A capstone (or keystone) is the wedge-shaped stone at the top of an arch. Roman architecture was one of the greatest achievements of Roman civilization, and Rome’s architects and engineers had developed the arch into their trademark. An arch or series of arches was not only beautiful, but it provided a brilliant way to pierce a load-bearing wall for doors or light without weakening the wall. The half circle of specially shaped stones was laid over a curved wooden form. When the capstone was mortared in on top, the wooden form could be removed. All the weight and stress from above the door or window was directed sideways through the stones of the arch and its capstone. The capstone might not look all that important. Knock out the capstone, however, and the arch would collapse, as well as the rest of the wall. In the same way, suffering Christians need to be reminded that Christ Jesus is the capstone of our lives. If he is knocked out of that position, our lives collapse. The “builders” in Psalm 118 refer to the religious leaders of the Israelite people. They chose to build their nation’s spiritual life without Christ. They rejected him because they did not like how he looked—he was nothing like the “messiah” they were expecting. They left him on the quarry floor and used other building materials. But their structure collapsed without him. In disgust over their rejection of his Son, the Father withdrew his hand of mercy and let the Romans take the nation apart.

Jeske, M. A. ©2002. James, Peter, John, Jude (p. 89). Milwaukee, WI: Northwestern Pub. House.

Isaiah 8:14

And he will become a sanctuary and a stone of offense and a rock of stumbling to both houses of Israel, a trap and a snare to the inhabitants of Jerusalem.

Jesus Christ does not like to be rejected and thrown on the ground. When that happens, the rejected capstone becomes a stumbling stone, that is, he will move himself to trip these proud builders so that they come crashing down. Christ promises unlimited blessings to all who put their trust in him. But he promises unlimited curses on those who disobey and disbelieve the gospel message. There is no middle ground—either Christ is the cornerstone and capstone of your life or he is a stumbling stone, a fearsome boulder, an implacable enemy who will take you down.

Jeske, M. A. ©2002. James, Peter, John, Jude (p. 90). Milwaukee, WI: Northwestern Pub. House.

In the Church, our own hymnody has taken up the imagery of the Messiah as a Stone as well with songs that run through the mind on a loop when reading this passage. May the Rock of our Salvation walk with you. (And yes, I see the irony of that prayer.)

Christ Is Our Cornerstone

Christ is our cornerstone, On Him alone we build;
With His true saints alone, The courts of heaven are filled.
On His great love Our hopes we place
Of present grace And joys above.

Built on the Rock

Built on the Rock the Church shall stand
    Even when steeples are falling.
Crumbled have spires in every land;
    Bells still are chiming and calling,
Calling the young and old to rest,
But above all the souls distressed,
    Longing for rest everlasting.

We are God’s house of living stones,
    Built for His own habitation.
He through baptismal grace us owns
    Heirs of His wondrous salvation.
Were we but two His name to tell,
Yet He would deign with us to dwell
    With all His grace and His favor.