The gospel message is in its most simple form the offer and the promise to be unified with Christ. Jesus suffered and died on the cross to unify us with Himself and then put us in the position to give us all that is His. You could wrestle with all of the ramifications of that statement for all of eternity… and you will! 2 Cor 2.15-24 refers again and again to our oneness with Jesus.
Paul ends this paragraph with one aspect of our unity with Jesus stating that “God is the one who irreversibly and constantly keeps us unified with Christ.” (vs 21) The word translated here as “irreversibly and constantly keeps us” is often translated “establishes.” It is a present tense Greek verb meaning that is continual and constant action. It would not be overstating it to say that God never stops keeping believers in unity with His Son.
The word “βέβαιος ” means “to make secure or to firmly establish.” It was often used in contemporary Greek usage to mean “a guarantee of a sale.” In the OT (LXX) it was used to describe the immutable nature of the promises of God AND God Himself.
The takeaway is undeniable. Paul states here that as God Himself is unchanging so sure is the guarantee that God will never stop keeping His own in unity with His Son. How powerful is the work of Christ on the cross? So powerful that God would have to change his very nature and be in conflict with His own character to stop -even for a moment- keeping us in oneness with His Son. God continually and irreversibly keeps you in union with Jesus… and NOTHING will ever stop that from being true!