Jesus is recommending persistence in prayer (Augustine).
Those who pray continually have an advocate with the Father, who gives them whatever they ask (Origen).
In the parable a persistent widow will be blessed because she seeks out her judge with persistence (Cyril).
The persistent prayer of the widow transforms the iniquity and wickedness of the judge into mercy because she was more persistent than he was (Ephrem).
God has promised salvation to the elect, who cry to Him day and night, from the attacks of the Satan their adversary (Martyrius).
Our enemy is none other than Satan. We have to pray constantly and confidently. We have to ask, seek and persevere. Will there be a faithful community awaiting at the coming of the Son of Man amidst all the false teachings? (Cyril).