1 He also spoke a parable to them that they must always pray, and not give up, 2 saying, “There was a judge in a certain city who didn’t fear God, and didn’t respect man. 3 A widow was in that city, and she often came to him, saying, ‘Defend me from my adversary!’ 4 He wouldn’t for a while, but afterward he said to himself, ‘Though I neither fear God, nor respect man, 5 yet because this widow bothers me, I will defend her, or else she will wear me out by her continual coming.’”

6 The Lord said, “Listen to what the unrighteous judge says. 7 Won’t God avenge his chosen ones, who are crying out to him day and night, and yet he exercises patience with them? 8 I tell you that he will avenge them quickly. Nevertheless, when the Son of Man comes, will he find faith on the earth?”

9 He spoke also this parable to certain people who were convinced of their own righteousness, and who despised all others. 10 “Two men went up into the temple to pray; one was a Pharisee, and the other was a tax collector. 11 The Pharisee stood and prayed to himself like this: ‘God, I thank you, that I am not like the rest of men, extortionists, unrighteous, adulterers, or even like this tax collector. 12 I fast twice a week. I give tithes of all that I get.’ 13 But the tax collector, standing far away, wouldn’t even lift up his eyes to heaven, but beat his breast, saying, ‘God, be merciful to me, a sinner!’ 14 I tell you, this man went down to his house justified rather than the other; for everyone who exalts himself will be humbled, but he who humbles himself will be exalted.”

via World English Bible Luke 18.

Why wouldn’t these two parables be about the same thing? The widow bothering the judge is the tax collector asking for mercy. The Pharisee boasting in himself is the oppressive adversary.