Paul talked about understanding that all the saints are built on the foundation of the apostles and prophets with Jesus Christ Himself being the Chief Cornerstone. The foundation came from the prophets in the Old Testament as they looked ahead to the coming of the Messiah. The apostles understood, by the Holy Spirit, what the prophets had prophesied so they laid the foundation for the house of God which was made up of believers who were called living stones by Peter in (1 Peter 2:5). Everything must be squared with Christ, the Chief Cornerstone, for the building to be perfectly lined up. Paul wrote:
In whom the whole building, being fitted together, grows into a holy temple in the Lord, in whom you also are being built together for a dwelling place of God in the Spirit.
Ephesians 2:21–22 NKJV
Paul used words like fitted, grows, and built with great intention. In another place he used the words “every joint supplies.” Through the different metaphors, Paul drove the point home that we are not independent from one another. God fits us with other saints who are also fitted. As we picture an army, we see one fighting unit and not just individual soldiers fighting independently. The spiritual battle in which we are engaged is no different. It is meant to be fought together with other believers, as a well-trained unit in rank and file.