In ancient construction the most important piece of a building was the cornerstone. It served many functions, but it’s greatest function was as a reference for every other stone that would be laid in the building. Once the cornerstone was laid, every other stone would be laid based on its position. Because of this, the stone had to have perfect dimensions, and perfect angles, and had to be laid with precision. If not, then the walls would be out of square horizontally, or even worse, they would be out of plumb vertically. In the first case, the building wouldn’t fit together properly, and in the second, the walls would lean and collapse on themselves.
God used this truth about how buildings are constructed to provide a prophetic metaphor to his people. This metaphor was so important and useful that God repeated it multiple times throughout the Old Testament. That metaphor has as much relevance today as when it was first uttered. One of its best formulations is found in Psalm 118:22-24 where it serves as a prophecy of Jesus. The psalmist writes that the stone that the builders rejected has become the cornerstone.
Jesus, the only perfect man was rejected by the social forces of his day. They did not recognize him, and wished to build their spiritual and religious edifice upon their own traditions and rules. But Jesus, an immovable rock, was not the rock they wanted. So God used the stone of Jesus to crush the religious order of the day. Jesus even referenced the Psalm 118 prophetic metaphor when he warned those religious leaders that the cornerstone would crush and break to pieces those who rejected it (Luke 20:18).
God then began to build a new religious order on the cornerstone of Jesus and his example. The true church of God is built on nothing less than Jesus Christ and his righteousness.
This metaphor doesn’t just apply to the church collectively, but it also applies to its members individually. What is the cornerstone of your life? How are you laying your stones in reference to it? Are the walls you’ve built square and true? If not, it may be that you are building on a wrong foundation, and on a wrong plumb line.