2 Corinthians 13:5

Unless indeed ye be reprobate (ei mhti adokimoi este). Paul challenged his opposers in Corinth to try (peirazete) themselves, to test (dokimazete) themselves, whether they were "in the faith" (en th pistei), a much more vital matter for them than trying to prove Paul a heretic. Such tests can be made, unless, alas, they are "reprobate" (adokimoi, the very adjective that Paul held up before himself as a dreadful outcome to be avoided, 1 Corinthians 9:27 ).