Jesus Christ is building His Church. When He was on earth, He said, "I will build my church; and the gates of hell shall not prevail against it" (Matt. 16:18).
We are living stones within God's building, and we also have a part as co-builders as we take the Gospel to others so they can receive Christ as Saviour.
Christ came and preached peace; now we who know Him as Saviour are to preach the Gospel to others so they may have this peace. Jesus told the Father, "As thou hast sent me into the world, even so have I also sent them into the world" (John 17:18).
Just before Jesus ascended to the Father, He gave believers the Great Commission: "All power is given unto me in heaven and in earth. Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost: teaching them to observe all things whatsoever I have commanded you: and, lo, I am with you alway, even unto the end of the world. Amen" (Matt. 28:18-20).
Those who receive Christ as Saviour become living stones, precisely fitted into the building of God. Just as there are many shapes and sizes of stones, so individual believers vary from one another, but God has a special place for each in the building.
Those in Paul's day knew that it took much work to shape stones so they would fit precisely in a building. So Paul was emphasizing not only that believers are stones in God's building but also that it takes the shaping work of God to make them fit properly into the building.
The harder the stone, the longer it takes the builder to make it what he wants it to be. As living stones we sometimes find the process painful, but the end result is good.
That's why Romans 8:28 says, "And we know that all things work together for good to them that love God, to them who are the called according to his purpose."
"Know ye not that ye are the temple of God, and that the Spirit of God dwelleth in you?" (1 Cor. 3:16).