Question: "What does it mean that Jesus Christ is the cornerstone?"
Answer: Since ancient times, builders have used cornerstones in their construction projects. A cornerstone was the principal stone, usually placed at the corner of an edifice, to guide the workers in their course. The cornerstone was usually one of the largest, the most solid, and the most carefully constructed of any in the edifice. The Bible describes Jesus as the cornerstone that His church would be built upon. He is foundational. Once the cornerstone was set, it became the basis for determining every measurement in the remaining construction; everything was aligned to it. As the cornerstone of the building of the church, Jesus is our standard of measure and alignment.
The book of Isaiah has many references to the Messiah to come. In several places the Messiah is referred to as “the cornerstone,” such as in this prophecy: “So this is what the sovereign Lord says: ‘See, I lay a stone in Zion, a tested stone, a precious cornerstone for a sure foundation; the one who trusts will never be dismayed. I will make justice the measuring line and righteousness the plumb line’” (Isaiah 28:16–17). In context, God speaks to the scoffers and boasters of Judah, and He promises to send the cornerstone—His precious Son—who will provide the firm foundation for their lives, if they would but trust in Him.
In the New Testament, the cornerstone metaphor is continued. The apostle Paul desires for the Ephesian Christians to know Christ better: “Consequently, you are no longer foreigners and aliens, but fellow citizens with God’s people and members of God’s household, built on the foundation of the apostles and prophets, with Christ Jesus himself as the chief cornerstone. In him the whole building is joined together and rises to become a holy temple in the Lord” (Ephesians 2:19– 21). Furthermore, in 1 Peter 2:6, what Isaiah said centuries before is affirmed in exactly the same words.
Peter says that Jesus, as our cornerstone, is “chosen by God and precious to him” (1 Peter 2:4). The cornerstone is also reliable, and “the one who trusts in him will never be put to shame” (verse 6).
Unfortunately, not everyone aligns with the cornerstone. Some accept Christ; some reject Him. Jesus is the “stone the builders rejected” (Mark 12:10; cf. Psalm 118:22). When news of the Messiah’s arrival came to the magi in the East, they determined to bring Him gold, frankincense, and myrrh. But when that same news came to King Herod in Jerusalem, his response was to attempt to kill Him. From the very beginning, Jesus was “a stone that causes people to stumble and a rock that makes them fall” (1 Peter 2:8).
How can people reject God’s chosen, precious cornerstone? Simply put, they want to build something different from what God is building. Just as the people building the tower of Babel rebelled against God and pursued their own project, those who reject Christ disregard God’s plan in favor of their own. Judgment is promised to all those who reject Christ: “Anyone who falls on this stone will be broken to pieces; anyone on whom it falls will be crushed” (Matthew 21:44).