A.T. Robertson Commentary Luke 18:3

"and there was a widow in that city; and she came oft unto him, saying, Avenge me of mine adversary." — Luke 18:3 (ASV)

Came oft (ηρχετο). Imperfect tense denotes repetitions, no adverb for "oft" in the Greek.

Avenge me of (εκδικησον με απο). A late verb for doing justice, protecting one from another (note both εκ and απο, here). Deissmann (Light from the Ancient East, pp. 420ff.) quotes a στηλη of the second century B.C. with a prayer for vengeance for a Jewish girl that had been murdered which has this very verb εκδικεω.