"Test yourselves to see if you are in the faith; examine yourselves! Do you not recognize this about yourselves, that Jesus Christ is in you-unless you indeed fail the test?" (2Co 13:5). The prepostion "in" denotes a location or place with certain defined boundaries. It could also mean you agree with some proposed truth and take it further by identifying with it. Therefore if "Christ is in you" (:5) you are of "those who are in Christ Jesus" (Ro 8:1). It is not designating a physical place per se. But it depends on "if you are in the faith" (1Co 13:5). When a person "believes in Him who justifies the ungodly, his faith is credited as righteousness" (Ro 4:5). Paul concludes "I trust that you will realize that we ourselves do not fail the test" (2Co 13:6).
How do you conduct this self-test? You must know what it means to be "in the faith" (:5). When you believed "you were sealed in Him with the Holy Spirit of promise who is given as a pledge of our inheritance" (Eph 1:13-14). You are now "in Him" (:13) which is your position. "Do you not know that you are a temple of God, and that the Spirit of God dwells in you?" (1Co 3:16). "If Christ is in you" (Ro 8:10) you are "in the Spirit, if indeed the Spirit of God dwells in you" (:9). Therefore "God abides in him" (1Jn 4:15). To abide means to stay or remain in a permanent relationhip. "We know that we abide in Him and He in us, because He has given us His Spirit" (4:13). It is "this mystery . . . which is Christ in you, the hope of glory" (Col 1:27).
It is "He who raised Jesus from the dead . . . who indwells you" (Ro 8:11). Christ "was declared the Son of God with power by the resurrection of the dead" (1:4). "After listening to the message of truth" (Eph 1:13) "you have heard Him and have been taught in Him, just as truth is in Jesus" (4:21). "Let that abide in you which you heard from the beginning . . . [and] you also will abide in the Son and in the Father" (1Jn 2:24). But unless the "Spirit of God dwells in you . . . [for] if anyone does not have the Spirit of Christ, he does not belong to Him" (Ro 8:9). "Whoever confesses that Jesus is the Son of God, God abides in him, and he in God" (1Jn 4:15).