Ephesians 2:21 (ESV) … “in whom the whole structure, being joined together, grows into a holy temple in the Lord.”
The stones are forming a living, spiritual temple to glorify the Lord. In the Old Testament, the presence and glory of God inhabited a literal stone building. Now God dwells not in a stone building but in the hearts of believers. Christ is the unifying factor that takes the separate stones and creates a temple. This temple is holy, set apart for God. In this temple God receives worship and praise. The hearts of believers is thus the basic worship place in God’s kingdom on earth.
Paul does not mention stones specifically in our text, but that is what he is thinking of when he writes, “And in him you too are being built together to become a dwelling in which God lives by his Spirit” (v. 22). Believers are mortared together with Christ, as God the architect through his workmen, the preachers of the gospel, builds his church. Peter said it in the verse just before those I have quoted: “You also, like living stones, are being built into a spiritual house to be a holy priesthood, offering spiritual sacrifices acceptable to God through Jesus Christ” (1 Peter 2:5).
The applications of this part of the picture are so obvious as hardly to need elaboration. Let me suggest a few. First, the stones placed into this great structure are chosen and shaped for their position by God. It is his temple; he is the architect; it is not for us to determine where we will fit in or how. Second, the stones are placed into position in relationship to Jesus Christ. They are attached to him; if they are not, they are not part of this building. Third, the stones are of different shapes and sizes, perhaps even of different material, and they are employed for different functions. Some serve in one way, some another. Fourth, the stones are linked to one another. From where they are placed they cannot always see this; they cannot always even see the other stones. But they are part of one interlocking whole regardless. Fifth, the stones of the temple are chosen, shaped, and placed, not to draw attention to themselves, but to contribute to a great building in which God alone dwells. Sixth, the placing of each stone is only part of a long work begun thousands of years in the past that will continue until the end of the age when the Lord returns.
What a great process this is! And how mysterious! We are told in 1 Kings 6:7 that when the great temple of Solomon was constructed “only blocks dressed at the quarry were used, and no hammer, chisel or any other iron tool was heard at the temple site while it was being built.” To my knowledge, no building in history was ever built in this way. Its construction was almost silent, so holy was the work. Silently, silently the stones were moved and added, and the building rose.
Thus it is with the church. We do not hear what is going on inside human minds and hearts as God the Holy Spirit creates new life and adds those individuals to the temple he is building. But God is working. In the days of the apostles God was adding Gentiles to a temple composed at that time largely of Jewish believers. He was adding Luke, Lydia, Phoebe, Philemon, Onesimus—and the believers at Ephesus, and other Greek and Roman cities. Later he added those we call the early church fathers, then the later church fathers and those to whom they ministered. At the time of the Reformation he added Luther and Calvin and Zwingli and Knox and Cranmer and many others. He is still adding to his temple today.
 Anders, M. (1999). Galatians-Colossians (Vol. 8, p. 115). Nashville, TN: Broadman & Holman Publishers.  Boice, J. M. (1988). Ephesians: an expositional commentary (p. 93). Grand Rapids, MI: Ministry Resources Library.