The Meaning of The Phrase "IN Christ"
We as believers are literally joined to the Lord Jesus Christ as our new life and identity.
17 Therefore if any man be in Christ, he is a new creature: old things are passed away; behold, all things are become new. 2 Corinthians 5:17 (KJV)
It is obvious that we cannot physically put one person into another person. Thus, being “in Christ” speaks of the believer’s literal ‘spiritual union with Christ,’ being as one with His very life which is ‘Spirit.’ We thereby one with Christ in nature … now at the core of our being… ‘in our spirit.’ Believers then are not as they were before they first believed, they are indeed have become “new creature,” then bearing Christ’s resurrected “Spirit of life,” with His mind emotion and will in their… “spirit of man.” These two spirits have then become “one spirit” (1Cor 6:17).
The word “in” here above is the Greek word “ev.” Strong’s 1722 denoting a fixed position (in place, time or state), a relation of rest. It is used 146 times in the New Testament as: “in Christ,” “in Him,” “in whom,” “in the beloved,” etc. it means one with, joined to, or in union with. These are most often found in the Apostle Paul’s 13 epistles.
This speaks of a person to whom Another (Christ) is wholly joined and to whose power and influence he is subject. The world “in” is used as such in the writings of Paul concerning every believer in the “gospel of the grace of God” (Acts 20:24).
By weight of scripture alone, “in” occurs more frequently in the epistles than love, faith, grace, hope.
“The Spirit of life in Christ Jesus” (Rom. 8:2a) is the resurrected Christ now entirely in His Spirit form, while still bearing the marks of His humanity and His human experience of the suffering and death of the Cross, which was on our behalf. The “Spirit of life in Christ Jesus” then permits Christ to be joined to our “spirit of man” … making us “one spirit” with Him.
Thus, Paul wrote: 17 But he that is joined unto the Lord is one spirit. 1 Corinthians 6:17 (KJV)
Thus, today Christ indwells the members of “His body” which Paul calls “the church, which is His body” (Eph. 1:22b-23a). This joining of spirit was accomplished when thew Holy Spirit baptized each and every believer into Christ’s body the moment they first believed.
13 For by one Spirit are we all baptized into [wholly set into the] one body [of Christ], whether we be Jews or Gentiles, whether we be bond or free; and have been all made to drink into one Spirit. 1 Corinthians 12:13 (KJV)
We as believers are partakers of Christ’s eternal divine life and of His eternal elevated resurrected humanity.
So, when Paul says we are “in Christ” it means we are Joined To and One With the very Person of Christ as He now is, whereby we are “flesh of His flesh” and “bone of His bone” … while we are still in this present world … as His “ambassadors.”
20 Now then we are ambassadors for Christ, as though God did beseech you by us: we pray you in Christ's stead, be ye reconciled to God. 2 Corinthians 5:20 (KJV)