Ephesians 5:31-32 English Standard Version 

31 “Therefore a man shall leave his father and mother and hold fast to his wife, and the two shall become one flesh.” 32 This mystery is profound, and I am saying that it refers to Christ and the church.

Which is it, our big brother or our betrothed?

What is the profound mystery?

The answer to the first question is both. The adoption into the family of God is stated as a current condition. We are in our current state being conformed. Betrothed however is related to a future state which will remain in effect until the wedding feast. Both are based on promises made by God which are conditional.

The first is justification by faith placed in the finished works of Christ. We have no say in the matter. Everything related to our justification and sanctification is the purview of God the Father and God the Father alone.

The second is one of betrothal that indicates a matter of gracious endeavors bestowed upon us as members of the body of Christ, His universal church, His betrothed. These gracious endeavors are identified in gifts and talents for the sole purpose of building and bettering His Church. 

While we have no say in the adoption process, we do have a say in the betrothal process. We have a relationship with the bridegroom and that requires communication. We cannot do what is asked of us unless we first hear His instructions, understand those instructions and love Him enough to carry out those instructions.

The reason we have no say in the adoption process is because that status never changes. There is nothing we can do to alter that condition.

The status of the bride is expected to change. While His love and commitment to His bride is inviolate, the betrothed is expected to grow closer to the bridegroom and learn to love Him in ways the world could never teach us. That is not a matter of flesh, it is pure spirit.

That is where the great mystery comes into play.