This parable has rightly been described by theologians as the most difficult & puzzling passage. My interpretation is made with the help of this article A History of Recent Interpretation of the Parable of the Unjust Steward, by Dennis Ireland, which is an abridged form of his first chapter of his PhD. dissertation, "Stewardship and the Kingdom of God: An Exegetical and Contextual Study of the Parable of the Unjust Steward in Luke 16:1-13".
Negative Example Interpretation
Some have interpreted it as a negative example in that there is nothing worthy of imitation in the steward. In the course of the recent history of interpretation several interpreters of our parable have argued that irony is the key to its understanding. They agree that the parable is a negative example for Christians, but this has been conveyed by Jesus in the form of irony, especially in vv 8-9. P. G. Bretscher (1951) puts his finger on the interpretive crux of our parable when he observes that, on the analogy of faith, vv 8-9 (where the steward is commended and the disciples are exhorted to "use worldly wealth to gain friends" for themselves) are the opposite of what one would have expected Jesus to say. The way out of this difficulty, he suggests, is to "read into the voice of Jesus as He utters the words of verses 8 and 9 the overtones of deepest irony."
While it is a common and ingenious trick to undermine the word of God by turning it into sarcasm, satire & irony, to argue it doesn't mean what it says, according to the example and spirit of "You will not surely die." Gen 3:4. Simply turn God into a joker. I can give Bretscher the benefit of doubt here, since it is a difficult passage and not a plain command. For it is difficult to make sense of why does he say to make friends using unrighteous wealth. It seems he is approving of the unrighteous wealth, thus approving fraud and corruption.
The Right interpretation
According to Dennis Ireland, the most common way to justify the steward's actions toward the debtors is by appealing to the socioeconomic background of the parable. Among the first to have done so was J. J. Oosterzee in Lange's commentary, in 1859. Oosterzee explains that steward had been charging excess from the debtors, taking high rates of rent. The master saw that the accounts don't tally, there should have been more profit according to the transactions. The final debt reduction, therefore, was not falsification of the accounts (to which the master unnaturally shows mercy and even commends him for), but it was a rectification of the past wrongs. The debt reduction was being paid by the theft portion itself, and thus, he was not defrauding the master in doing so. This is why the master perfectly approves of the discount, he is not showing mercy by allowing him to steal more.
This right interpretation has been extended or developed further by M. D. Gibson, "On the Parable of the Unjust Steward," ExpTim 14 (1902-3), by P. Gachter, and J. D. M. Derrett who used the ancient Jewish cultural context to explain rather than the contemporary and eastern culture parallels.
Lesson
The reason why the master commends and approves of the debt reduction is because of the Steward's shrewdness for repaying the debtors of the fraud that they will accept him as friend. The debtors won't know that they had been defrauded by this man, but on seeing the great generosity in debt reduction or discount, they will gladly help him, as they owe him the favour. The parable doesn't show the Steward rectifying his fraud out of moral reasons due to repentance, but only for his shrewd, wise self interest for survival. He is an example of the sons of this age, the corrupt people, he was an unrighteous man. His act of returning the unrighteous wealth was only incidental to his shrewdness, but nonetheless it was a righteous act.
Jesus is teaching shrewdness for survival and other necessary righteous self-interests. The lesson is not to become unrighteous, but to spend your unrighteous wealth (if any) for good purpose like returning those whom you have defrauded or by making good friends from it or by simply doing charity. The children of the light should learn to be wise and clever like serpents. The children of the light should not live as fools and naive people, but wise like this fraud manager. The goal for shrewdness is not social and monetary possessions, but for righteous purpose only. Doing favours for others may surely prove to be life saving at times and can help in obtaining favourable outcomes for any in need. Survival for the end times was the need of that hour, however, the parable is not solely meant for the eschatological context. The negative-example and the eschatological angle interpretations are way off the mark.
If then you have not been faithful (to God) in the unrighteous wealth, who will entrust to you the true riches? And if you have not been faithful in that which is another's, who will give you that which is your own?
Zacchaeus, the tax collector was surely a living parallel example of how he gave up all his unrighteous wealth. The rich young ruler of Luke 18 was a negative example who could not give up his unrighteous wealth.
[Luke 19:2, 8-10 ESV] And behold, there was a man named Zacchaeus. He was a chief tax collector and was rich.... Zacchaeus stood and said to the Lord, “Behold, Lord, the half of my goods I give to the poor. And if I have defrauded anyone of anything, I restore it fourfold.” And Jesus said to him, “Today salvation has come to this house, since he also is a son of Abraham. For the Son of Man came to seek and to save the lost.”
