Since the Gnostics already knew what the text meant, they were no longer constrained by what the text "said"

This refusal to subscribe to a literal understanding of the text was a source of perennial frustration for the proto-orthodox church fathers. ... Since the Gnostics already knew what the text meant (Christ had told them!) they were no longer constrained by what the text "said" (or at least what the orthodox said it said)

B. D. Ehrman, The orthodox corruption of scripture (1993), 123