Who concerning the truth have erred, saying that the resurrection is past already; and overthrow the faith of some.
Erred, х eestocheesan (G795)] - 'missed the aim' (note 1 Timothy 6:21).
Is past already - has already taken place. The beginnings of Gnostic heresy already existed. They "wrested" (2 Peter 3:16) Paul's words (Romans 6:4; Ephesians 2:6; Colossians 2:12), "to their own destruction;" as though the resurrection was merely the spiritual raising of souls from the death of sin. Compare 1 Corinthians 15:12, etc., where he shows all our hopes rest on the literal reality of the resurrection. To believe it past (as the Seleucians or Hermians did, according to Augustine, Ep. 119: 55, 'Ad Januarium,' sec. 4) is really, to deny it.
Overthrow - subvert "the foundation" on which alone faith can rest (2 Timothy 2:19: cf. Titus 1:11).