A.T. Robertson Commentary 2 Timothy 3:8

"And even as Jannes and Jambres withstood Moses, so do these also withstand the truth. Men corrupted in mind, reprobate concerning the faith." — 2 Timothy 3:8 (ASV)

Like as (ον τροπον). "In which manner." Adverbial accusative and incorporation of the antecedent τροπον into the relative clause.

Jannes and Jambres (Ιαννης κα Ιαμβρης). Traditional names of the magicians who withstood Moses (Targum of Jonathan on Ex 7:11).

Withstood (αντεστησαν). Second aorist active (intransitive) of ανθιστημ, to stand against, "they stood against" (with dative Μωυσε). Same word used of Elymas in Ac 13:8 and repeated here ανθισταντα (present middle indicative). Paul here pictures the seducers of the γυναικαρια above.

Corrupted in mind (κατεφθαρμενο τον νουν). Perfect passive participle of καταφθειρω, old compound, in N.T. only here in critical text. See 2 Corinthians 11:3; 1 Timothy 6:5 for διαφθειρω. The accusative νουν is retained in the passive.

Reprobate (αδοκιμο). See 1 Corinthians 9:27; Titus 1:16. They had renounced their trust (πιστιν) in Christ.