ἐν Χριστῷ en Christō — "in Christ"
To be "in Christ" is to be united to Jesus Christ by faith, so that what belongs to Him becomes the believer’s saving reality.
This phrase keeps salvation Christ-centered rather than man-centered. Election is in Christ, redemption is accomplished by Christ, calling joins us to Christ, justification is because of Christ, sanctification flows from Christ, and glorification is secured in Christ.
Your entire saving identity is no longer defined by Adam, sin, law-condemnation, flesh, or the present evil age. It is defined by union with the crucified, risen, and reigning Christ.
ἐν Χριστῷ ("in Christ") occurrences in Romans
The Believer's Identity in Christ
Union with Christ — A Layman's Summary
What It Means to Be United to Jesus
In Christ — The Pauline Witness