"Then [Jesus] spoke a parable to them, that men always ought to pray and not lose heart, saying: 'There was in a certain city a judge who did not fear God nor regard man. Now there was a widow in that city; and she came to him, saying, "Get justice for me from my adversary." And he would not for a while; but afterward he said within himself, "Though I do not fear God nor regard man, yet because this widow troubles me I will avenge her, lest by her continual coming she weary me."' Then the Lord said, 'Hear what the unjust judge said. And shall God not avenge His own elect who cry out day and night to Him, though He bears long with them? I tell you that He will avenge them speedily. Nevertheless, when the Son of man comes, will He really find faith on the earth?'" (Luke 18:1-8).
The purpose of this parable was to encourage Jesus' followers that they "always ought to pray and not lose heart." It is implied that some do tire of prayer. Perhaps this happens because of circumstances or because of a seeming failure to obtain an answer they desire. One must work to maintain a good prayer life during both good and bad times (cf. I Thess. 5:17; Rom. 12:12). Our prayer life, to a large degree, is an indicator of how much faith we have. The subject of this parable is related to the topic Jesus was discussing at the end of Luke 17 (i.e., the second coming; cf. 18:8).
We are first introduced to "a judge who did not fear God nor regard man." The law of Moses required that there be judges to administer impartial justice in every city (cf. Exo. 18:21; Deut. 16:18). This man was definitely not qualified to be a judge! He had no reverence for God and he didn't have any respect for mortals either. Admittedly, he was very honest about his unrighteousness (cf. Luke 18:4), but there is no merit in being an honest enemy of God!
The widow begged - "Get justice for me from my adversary." She knew this was the proper thing to do and likely had no other options anyway (cf. Deut. 27:19). The judge would not seek justice for the woman at first. This is certainly because he disregards anyone but himself. This widow was without influence and unable to offer a bribe; thus, she had little to hope for from this wicked judge.
Eventually, the judge agreed to avenge the widow lest she keep bothering him and wear him out by her continual coming. His reasoning was entirely selfish. He didn't care one bit about justice. He just wanted to get rid of this "pesky" woman.
The meaning of the parable is as follows: The judge represents God and the widow represents mankind. Widowhood is symbolic of defenselessness, and without God humans are defenseless and without hope. Those who have obeyed the gospel are God's "elect" and need to rely upon God for justice from their adversaries (cf. Rom. 12:19). One might rightly wonder how God could be symbolized in any way by a wicked judge. The key here is realizing that this parable is an argument in contrasts. If a wicked human judge will eventually render justice because one keeps coming to him, how much more will a loving, righteous God avenge His children who cry out to Him!
It needs to be understood that while God does expect persistence in our prayers (cf. Luke 18:1; 11:8), we should not think that the only way God will answer us is if we kick His door down by our persistence. God is always here for us and does not have to be motivated to help us. Thus, we should call upon Him with confidence (cf. I Peter 3:12; I John 3:22). That is not to say that He will answer us in the way we expect or in the time frame we desire, but we can have the assurance that He will do what is best.
"[God] bears long with them" - This is an important point in the parable. From our earthly perspective, it may often seem that our cries to God for justice are falling on deaf ears. May we come to understand that just as God is patient with us and our shortcomings, He also bears with our adversaries! He delays executing vengeance upon them because of the fact that He is longsuffering and doesn't want any to perish (cf. II Pet. 3:9). He gives the wicked sufficient time to repent so that they may be saved, but in so doing the righteous are tried, and some will lose heart, thinking that God has either forgotten or doesn't care (cf. Gal. 6:9; Matt. 24:12,13).
Although God is longsuffering, He will not delay forever in avenging the righteous (cf. Rev. 6:10). When He does deliver justice he will do so "speedily"; that is, in a quick manner (though not necessarily soon). We need to have confidence in God as a righteous judge who will bring swift destruction upon the wicked at the second coming, as He did in the flood and the destruction of Sodom.
"When the Son of Man comes, will He really find faith on the earth?" (Luke 17:8). When Jesus comes again will He really find those who patiently persist in prayer, even while they endure persecution from their enemies (cf. I Thess. 4:17)? Or, will He find those who have lost heart and given up on prayer (and on God)? May we learn to be patient in prayer until the Lord's return!