There are many unions all over the world, but in only one place is true unity to be found: in the Lord Jesus Christ. The children of fallen Adam have always been divided. Adam’s first two children could not get along together. One killed the other. And now that the race has multiplied there are now billions of separate, individual wills in the world. Some of Adam’s children try to get along together amicably and enjoy some measure of success, but this always takes effort. It does not come naturally. Even the dearest lovers must be prepared to yield to each other’s wishes frequently to get along well together. There is no true unity in this world.
But where Adam’s children have been divided by sin, they may be saved and truly united in Christ. As Christ became one with us when He died our death (the wages of sin) at Calvary, so we may become one with Him as in faith we acknowledge that that death was not His but ours. This is what the Apostle referred to when he asked:
“Know ye not, that so many of us as were baptized into Jesus Christ were baptized into His death?” (Rom. 6:3).
This verse does not refer to water baptism, for no one can be baptized into Christ — become one with Him — by a physical ceremony. The only way to become one with Him is to accept by faith the fact that He died our death on the cross. The meeting place must always be Calvary. And as we acknowledge His death as ours and become one with Him, we automatically become one with each other.
“For by one Spirit are we all baptized into one body” (I Cor. 12:13).
Unity in Christ is not something for which Christians are to strive. It is a fact of grace to be recognized and enjoyed by faith. True believers in and out of all denominations have been baptized into one body, whether or not they recognize this.
Now it is for us to appropriate and enjoy this unity in Christ, “endeavoring to keep the unity of the Spirit in the bond of peace” (Eph. 4:3) i.e., seeking to experience the unity which the Spirit has made. Only those who have been baptized into Christ by faith can appreciate the blessed oneness which believers may enjoy. source