This exhortation (to set our hope fully on the Day of the Messiah) is echoed throughout the parables, particularly the Parable of the Widow (cf. Lk. 18:1-8). The context of the parable is the suddenness of the Messiah’s coming (17:20-25) and the justice established in the days of Noah and Lot as a sign of the Day of the Lord (17:26-37). Thus, the point of the parable ultimately boils down to “faith” (18:8) in Jesus as Messiah and his appointment as judge of the heavens and the earth (cf. Jn. 5:22-29; Acts 10:42; 17:31; Rom. 14:9f; 2 Tim. 4:1-8; etc.).  - John P. Harrigan