A.T. Robertson Commentary 2 Corinthians 13:5

"Try your own selves, whether ye are in the faith; prove your own selves. Or know ye not as to your own selves, that Jesus Christ is in you? unless indeed ye be reprobate." — 2 Corinthians 13:5 (ASV)

Unless indeed ye be reprobate (ε μητ αδοκιμο εστε). Paul challenged his opposers in Corinth to try (πειραζετε) themselves, to test (δοκιμαζετε) themselves, whether they were "in the faith" (εν τη πιστε), a much more vital matter for them than trying to prove Paul a heretic. Such tests can be made, unless, alas, they are "reprobate" (αδοκιμο, the very adjective that Paul held up before himself as a dreadful outcome to be avoided, 1 Corinthians 9:27).